Reproducing device

ABSTRACT

A reproducing device ( 100 ) includes (i) an optical pickup ( 6 ) for irradiating, with reproduction light, an optical disk ( 1 ) which is a super-resolution medium, (ii) an RF signal processing circuit ( 9 ) for converting, into a reproduction signal, light which reflected off optical disk ( 1 ), (iii) an i-MLSE detecting section ( 141 ) for evaluating quality of the reproduction signal, and (iv) a spherical aberration correcting section ( 142 ) for correcting a spherical aberration by using a result of evaluation of the quality of the reproduction signal.

TECHNICAL FIELD

The present invention relates to a reproducing device capable ofreproducing information.

BACKGROUND ARTS

An optical disk serving as an optical recording medium includes atransmissive substrate having a given thickness so that the transmissivesubstrate covers a recording surface of the optical disk in order toprotect the recording surface. An optical pickup serving as aninformation reading section reads out recorded information from theoptical disk based on an amount of light which is reflected off therecording surface when the recording surface is irradiated with readingbeam light via the transmissive substrate.

Note, however, that in a case of producing optical disks, it isdifficult to form transmissive substrates of all of the optical disks sothat the transmissive substrates have thicknesses within a specifiedvalue, and this typically causes a thickness error of several μm. Such athickness error of the transmissive substrate causes a sphericalaberration. The occurrence of the spherical aberration causes a problemthat an amplitude level of an information reading signal and/or atracking error signal may be considerably decreases, and this thereforereduces accuracy of information reading. That is, in a case where anoptical disk is replaced with another optical disk, a thickness of atransmissive substrate changes, and this changes a spherical aberration.Accuracy of information reading is therefore reduced in a case where noprocess is carried out with respect to the spherical aberration thuschanged.

As such, in order to improve accuracy of information reproduction, it isnecessary to correct the spherical aberration. For example, PatentLiterature 1 discloses a technique of correcting such a sphericalaberration. According to the technique disclosed in Patent Literature 1,the spherical aberration is corrected so that an amplitude of an RF(Radio Frequency) signal becomes maximum.

CITATION LIST Patent Literature

Patent Literature 1

Japanese Patent Application Publication Tokukai No. 2004-145987(Publication date: May 20, 2004)

SUMMARY OF INVENTION Technical Problem

In recent years, an optical information recording medium is demanded tohave increased information storage capacity for processing an enormousamount of information, such as images. Examples of methods of meetingthe demand encompass a method using a super-resolution technique, whichis one of techniques of improving information processing to be carriedout during reproduction of the optical information recording medium.

The super-resolution technique is a technique of reproducing a signalhaving a mark length shorter than an optical system resolution limit (alimit determined based on (i) a laser wavelength and (ii) a numericalaperture of an optical system) of a reproducing device. Thesuper-resolution technique makes it possible to carry out recording byusing a shorter mark length, and this substantially increases arecording density. This is because it is not a recording technique but areproduction technique that matters when the recording density isincreased. Note that the optical system resolution limit is λ/4NA, where(i) λ indicates a wavelength of reproduction light irradiated from thereproducing device and (ii) NA indicates a numerical aperture of anobjective lens.

Note, however, that in a case where (i) a spherical aberration iscorrected, as disclosed in Patent Literature 1, so that an amplitude ofan RF signal becomes maximum and (ii) information recorded on an opticalinformation recording medium (super-resolution medium) reproducible bythe super-resolution technique is reproduced, a sufficient signalcharacteristic may not be obtained depending on shapes of pits which areprovided on the super-resolution medium. That is, in a case where (i)the spherical aberration is corrected by using a spherical aberrationcorrecting value obtained when a maximum amount of light (reflectedlight amount, return light amount) is reflected off the super-resolutionmedium irradiated with reproduction light and (ii) the informationrecorded on the super-resolution medium is reproduced, reliability ofthe information reproduction may deteriorate depending on the shapes ofthe pits which are provided on the super-resolution medium. Theinventors of the present application found that, as described above, asufficient signal characteristic may not be obtained depending on theshapes of the pits which are provided on the super-resolution medium.

The present invention has been made in view of the problems, and anobject of the present invention is to provide a reproducing devicecapable of accurately reproducing information recorded on unspecifiednumber of super-resolution media.

Solution to Problem

In order to attain the problem, a reproducing device in accordance withan aspect of the present invention is a reproducing device capable ofreproducing content from an optical information recording medium inwhich the content is recorded in a form of a pit group including one ormore pits shorter than an optical system resolution limit of thereproducing device, including: an irradiation section for irradiatingthe optical information recording medium with reproduction light; aconversion section for converting, into reproduction signal indicativeof the content, light which reflected off the optical informationrecording medium; a signal quality evaluating section for evaluatingquality of the reproduction signal converted by the conversion section;and a spherical aberration correcting section for correcting a sphericalaberration caused by the irradiation section, by using a result ofevaluation of the quality of the reproduction signal which quality hasbeen evaluated by the signal quality evaluating section.

In order to attain the problem, a reproducing device in accordance withan aspect of the present invention is a reproducing device capable ofreproducing content by irradiating, via an objective lens having anumerical aperture of 0.85, an optical information recording medium withreproduction light having a wavelength of 405 nm, the opticalinformation recording medium including (a) a light transmitting layerhaving a surface which the reproduction light enters, (b) an informationrecording layer which the reproduction light reflects off so thatinformation is reproduced, and (c) a substrate on which a pit group isprovided in a scanning direction, the pit group including one or morepits shorter than 119 nm which is an optical system resolution limit ofthe reproducing device, the light transmitting layer, the informationrecording layer, and the substrate being provided in this order from aside from which the reproduction light enters, the content beingrecorded in the information recording layer by use of the pit group,including: an irradiation section for irradiating the opticalinformation recording medium with reproduction light; a conversionsection for converting, into reproduction signal indicative of thecontent, light which reflected off the optical information recordingmedium; a signal quality evaluating section for evaluating quality ofthe reproduction signal converted by the conversion section; and aspherical aberration correcting section for correcting a sphericalaberration caused by the irradiation section, by using a result ofevaluation of the quality of the reproduction signal which quality hasbeen evaluated by the signal quality evaluating section.

In order to attain the problem, a reproducing device in accordance withan aspect of the present invention is a reproducing device capable ofreproducing content from an optical information recording medium having(i) a first region in which the content is recorded in a form of a firstpit group including one or more pits shorter than an optical systemresolution limit of the reproducing device and (ii) a second region inwhich medium identification information for distinguishing a type of theoptical information recording medium is recorded in a form of a secondpit group including pits each having a length not less than the opticalsystem resolution limit of the reproducing device, the reproducingdevice including: a first spherical aberration correcting section for,during reproduction of the content recorded in the first region,carrying out a process of correcting, by using a result of evaluation ofquality of a reproduction signal indicative of the content, a sphericalaberration caused by an irradiation section for irradiating the opticalinformation recording medium with reproduction light; and a secondspherical aberration correcting section for, during reproduction of themedium identification information recorded in the second region,correcting, by carrying out a process different from the process to becarried out by the first spherical aberration correcting section, thespherical aberration caused by the irradiation section.

Advantageous Effects of Invention

An aspect of the present invention brings about an effect of accuratelyreproducing information recorded on unspecified number ofsuper-resolution media.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a functional block diagram schematically illustrating aconfiguration of a reproducing device in accordance with Embodiment 1 ofthe present invention.

FIG. 2 is a view showing an example flow of how a reproduction operationis carried out with respect to an optical disk 1 in the reproducingdevice in accordance with Embodiment 1 of the present invention.

FIG. 3 is a view specifically showing an example of the process (processof correcting a spherical aberration) illustrated in FIG. 2.

FIG. 4 is a cross sectional view illustrating an optical disk inaccordance with Embodiment 1 of the present invention.

FIG. 5 is a plan view illustrating pre-pits provided on a substrate ofthe optical disk in accordance with Embodiment 1 of the presentinvention.

FIG. 6 shows, in (a) and (b), results of respective experiments fordemonstration which have been carried out with respect to two differentoptical disks which are similar to the optical disk in accordance withEmbodiment 1 of the present invention.

FIG. 7 is a functional block diagram schematically illustrating aconfiguration of a reproducing device reproducing device in accordancewith Embodiment 2 of the present invention.

FIG. 8 is a perspective view illustrating an external appearance of anoptical disk in accordance with Embodiment 3 of the present invention.

FIG. 9 is a plan view specifically illustrating a part of the opticaldisk illustrated in FIG. 9.

FIG. 10 is a functional block diagram schematically illustrating aconfiguration of a reproducing device in accordance with Embodiment 3 ofthe present invention.

FIG. 11 is a view showing an example flow of how a reproductionoperation is carried out, with respect to an optical disk, in thereproducing device in accordance with Embodiment 3 of the presentinvention.

FIG. 12 is a functional block diagram schematically illustrating aconfiguration of a reproducing device in accordance with Embodiment 4 ofthe present invention.

FIG. 13 is a perspective view illustrating an external appearance of anoptical disk in accordance with Embodiment 5 of the present invention.

FIG. 14 is a view schematically illustrating an example of stripes to beformed in a BCA (Burst Cutting Area) recording region 39 of the opticaldisk illustrated in FIG. 13.

FIG. 15 is a functional block diagram schematically illustrating aconfiguration of a reproducing device of Embodiment 5.

FIG. 16 is a flow chart showing an example flow of how a reproductionoperation is carried out, with respect to the optical disk, in thereproducing device in accordance with Embodiment 5 of the presentinvention.

DESCRIPTION OF EMBODIMENTS Embodiment 1

The following description discusses an embodiment of the presentinvention with reference to FIGS. 1 through 6. Note that “content,”described in Embodiment 1 and Embodiments 2 through 5 (later described),refers to information which is to be used by a user. Specific examplesof the content encompass (i) a static image such as a photograph, (ii) amoving image such as a movie, and (iii) a program.

<Configuration of Reproducing Device>

FIG. 1 is a functional block diagram schematically illustrating aconfiguration of a reproducing device 100 for reproducing an opticaldisk 1. The reproducing device 100 includes an optical pickup 6(irradiation section), a spindle motor 7, a focusing/tracking processingcircuit 8, an RF (Radio Frequency) signal processing circuit 9(conversion section), a focusing/tracking drive circuit 10, a focusingoffset adder circuit 12, a control section 14, and a memory 15.

The optical disk 1 is a read-only optical information recording medium(see FIG. 4 (later described)). In the optical disk 1, information suchas content is recorded in a form of a pit group which includes one ormore pits shorter than an optical system resolution limit of thereproducing device 100 or a reproducing device capable of reproducingthe optical disk 1. Note that a configuration of the optical disk 1 willbe later described. The optical disk 1 is driven and rotated by thespindle motor 7.

The optical pickup 6 irradiates, to the optical disk 1, laser beam light(optical beam) serving as reproduction light, so as to reproduce contentrecorded on the optical disk 1. The optical pickup 6 includes asemiconductor laser 61, a collimating lens 62, a beam splitter 63, a λ/4plate 64, a condensing lens 67, a light detector 68, a sphericalaberration correcting optical system 650, an optical system drivemechanism 651 for correction of spherical aberration, an objective lens660, and a focusing/tracking actuator 661.

The semiconductor laser 61 emits laser beam light having a given lightintensity (reproduction power). The laser beam light emitted from thesemiconductor laser 61 enters the spherical aberration correctingoptical system 650, via the collimating lens 62, the beam splitter 63,and the λ/4 plate 64.

The collimating lens 62 forms parallel light. The beam splitter 63splits the parallel light into transmitted light and reflected light.The λ/4 plate 64 dephases, by a quarter wavelength, a wavelength of thetransmitted light.

The spherical aberration correcting optical system 650 has a function ofcorrecting a spherical aberration caused by a thickness error of a lighttransmitting layer 4 (transmissive substrate, cover layer) of theoptical disk 1. The spherical aberration correcting optical system 650is, for example, a beam-expanding relay lens in which a concave lens 650a and a convex lens 650 b are combined. The spherical aberrationcorrecting optical system 650 is typically configured such that parallellight, which is obtained by expanding a beam diameter of parallel lightwhich has entered the spherical aberration correcting optical system650, exits from the spherical aberration correcting optical system 650.By changing a lens interval between the concave lens 650 a and theconvex lens 650 b, parallel light which enters the objective lens 660 isconverted into divergent light or focusing light. This causes aspherical aberration, caused by the objective lens 660, to be adjusted.

The optical system drive mechanism 651 adjusts a lens interval betweenthe concave lens 650 a and the convex lens 650 b. The optical systemdriving mechanism 651 allows the spherical aberration correcting opticalsystem 650 to carry out a function of correcting a spherical aberrationcaused by a variation in thickness of the light transmitting layer 4 ofthe optical disk 1.

The objective lens 660 converges, onto an information recording layer 3(see FIG. 4 (later described)) provided on the optical disk 1, laserbeam light which has exited from the spherical aberration correctingoptical system 650. The light detector 68 detects light which reflectedoff the optical disk 1.

The light detector 68 converts light, which reflected off the opticaldisk 1, into an electrical signal in accordance with an intensity of thelight which reflected off the optical disk 1. The light detector 68 thensupplies the electrical signal to each of the focusing/trackingprocessing circuit 8 and the RF signal processing circuit 9.

The focusing/tracking processing circuit 8 (i) generates a focusingerror signal (FES) and a tracking error signal (TES) and (ii) suppliesthe FES signal and the TES signal to the focusing/tracking drive circuit10.

The focusing/tracking drive circuit 10 generates a focusing drive signalin accordance with the FES signal. Further, the focusing/tracking drivecircuit 10 drives the focusing/tracking actuator 661 so as to carry outa focusing operation. In the focusing operation, the objective lens 660is displaced in a direction perpendicular to a disk surface of theoptical disk 1.

The focusing/tracking drive circuit 10 generates a tracking drive signalin accordance with the TES signal. Further, the focusing/trackingdriving circuit 10 drives the focusing/tracking actuator 661 so as tocarry out a tracking operation. In tracking operation, the objectivelens 660 is displaced in a radial direction (tracking direction) of theoptical disk 1.

Note that it is possible to employ, as a method of detecting a focusingerror signal, a well-known method such as an astigmatism method, a knifeedge method, or a spot size detection method. Note also that it ispossible to employ, as a method of detecting a tracking error, awell-known method such as a push-pull method, a DPP (DifferentialPush-Pull) method, or a DPD (Differential Phase Detection) method.

The RF signal processing circuit 9 converts, into a reproduction signal(RF signal) indicative of information (content), light that reflectedoff the optical disk 1 which was irradiated with reproduction light. Thereproduction signal thus converted is supplied to the control section 14(particularly, an i-MLSE (Integrated-Maximum Likelihood SequenceEstimation) detecting section 141).

The control section 14 controls the optical pickup 6, the spindle motor7, and servo systems. For example, in a case where the reproducingdevice 100 is loaded with the optical disk 1, the control section 14controls the spindle motor 7 so that the optical disk 1 is driven androtated under an operating condition in which, for example, a linearvelocity is constant or a number of revolutions is constant.

The control section 14 has a function of, for example, processingevaluation indices such as an i-MLSE, an amplitude of RF signal, andjitter. The control section 14 controls the memory 15 so that (i) aspherical aberration correcting value is stored/written therein and (ii)a spherical aberration correcting value is read out thereof. The memory15 stores therein initial setting values of the reproducing device 100.

After pre-processes (such as rotation of the optical disk 1 and turn-onof the semiconductor laser 61) end, the control section 14 controls thefocusing/tracking drive circuit 10 to start focusing control. In doingso, the focusing/tracking processing circuit 8 supplies, to thefocusing/tracking drive circuit 10, an FES signal which has beengenerated by carrying out a suitable process such as phase compensation.This causes the focusing/tracking drive circuit 10 to carry out thefocusing control.

The control section 14 controls the focusing offset adder circuit 12 tomake an offset adjustment of the focusing control. By adding an offsetto a servo control loop, a focusing state of a beam spot on the opticaldisk 1 is adjusted.

The control section 14 controls the focusing/tracking drive circuit 10to start tracking control. In doing so, the focusing/tracking processingcircuit 8 supplies, to the focusing/tracking drive circuit 10, a TESsignal which has been generated by carrying out a suitable process suchas phase compensation. This causes the focusing/tracking drive circuit10 to carry out the tracking control.

The control section 14 supplies a track jump signal to thefocusing/tracking drive circuit 10. This causes the focusing/trackingdrive circuit 10 to supply a track jump driving signal to a trackingcoil (not illustrated) provided in the focusing/tracking actuator 661.Thus, tracking jump control is carried out. Note that the focusingcontrol, the tracking control, and the tracking jump control can becarried out by respective suitable well-known methods.

The control section 14 includes the i-MLSE detecting section 141 (signalquality evaluating section) and a spherical aberration correctingsection 142. The RF signal processing circuit 9 converts, into anelectrical signal, light which reflected off the information recordinglayer 3 provided on the optical disk 1. In the RF signal processingcircuit 9, the electrical signal is subjected to processing, such asadjustment of a size of an electrical signal and AD conversion suitablefor various types of calculation to be carried out in the i-MLSEdetecting section 141. This causes the electrical signal to be convertedinto a reproduction signal. The RF signal processing circuit 9 suppliesthe reproduction signal to the i-MLSE detecting section 141. Operationsof the i-MLSE detecting section 141 and the spherical aberrationcorrecting section 142 will be described later in detail.

Note that, in the reproducing device 100, (i) reproduction light,emitted from the semiconductor laser 61, is set to have a wavelength of405 nm and (ii) an optical system, provided in the optical pickup 6, isset to have a numerical aperture (a numerical aperture (NA) of theobjective lens 660) of 0.85. Note, however, that Embodiment 1 is notlimited to this and it is therefore possible to set as appropriate, inaccordance with a type of the optical disk 1, a wavelength and anumerical aperture other than the wavelength of 405 nm and the numericalaperture of 0.85, respectively.

<Process of Reproducing Device>

FIG. 2 is a flow chart showing an example flow of how a reproductionoperation is carried out (control method and reproduction method) withrespect to the optical disk 1 in the reproducing device 100.

First, the reproducing device 100 is loaded with the optical disk 1(process S1). The control section 14 of the reproducing device 100recognizes, by use of a sensor (not illustrated) provided in the controlsection 14, that the reproducing device 100 is loaded with the opticaldisk 1.

Subsequently, after the control section 14 confirms that the reproducingdevice 100 is loaded with an optical disk 1, the control section 14controls the spindle motor 7 to rotate (process S2). This causes theoptical disk 1 to be driven and rotated under an operating condition inwhich, for example, a linear velocity is constant or a number ofrevolutions is constant. The control section 14 carries out varioussettings with respect to the reproducing device 100 in accordance withthe initial setting values stored in the memory 15.

Subsequently, the control section 14 controls the focusing/trackingdrive circuit 10 so that the objective lens 660 is focused on theinformation recording layer 3 of the optical disk 1, in whichinformation recording layer 3 information to be reproduced is recorded(process S3). The control section 14 then controls the focusing/trackingdrive circuit 10 to carry out tracking of the objective lens 660(process S4). That is, in the processes S3 and S4, the optical disk 1 isirradiated with the reproduction light from the optical pickup 6(irradiating step). This causes a reproduction signal to be generatedbased on light which reflected off the optical disk 1 (converting step).

Subsequently, the control section 14 corrects a spherical aberrationbased on an index (i-MLSE) indicative of signal quality (process S5;signal quality evaluating step, spherical aberration correcting step).The control section 14 then starts reproducing information recorded onthe optical disk 1, by using a spherical aberration correcting valuewhich has been determined in the process S5 (process S6). The followingdescription specifically discusses the process S5 with reference to FIG.3.

(Process Flow of Correcting Spherical Aberration)

FIG. 3 is a flow chart specifically showing an example of the process S5(process of correcting a spherical aberration) illustrated in FIG. 2.The following description discusses a process to be carried out afterthe RF signal processing circuit 9 supplies a reproduction signal to thei-MLSE detecting section 141 provided in the control section 14.

The i-MLSE detecting section 141 detects, in accordance with thereproduction signal supplied from the RF signal processing circuit 9, ani-MLSE value varying depending on a spherical aberration correctingvalue which is currently set (process S11). Subsequently, the i-MLSEdetecting section 141 stores, in the memory 15, the i-MLSE value thusdetected so that the i-MLSE value is associated with the sphericalaberration correcting value currently set.

Note that the i-MLSE refers to one of evaluation indices, which are usedto evaluate a signal characteristic of a reproduction signal ofinformation recorded at a high density. A reproduction signal has abetter signal characteristic as the i-MLSE value is smaller. The i-MLSEcan be also considered as an evaluation index similar to jitter, whichis a conventional evaluation index.

The spherical aberration correcting value refers to an amount which isused to correct a focusing position of an optical system which focusingposition has been displaced due to a spherical aberration. For example,in a case where the spherical aberration correcting value is 1 μm (−1μm), the optical system is to be corrected so that a focal point of theoptical system is brought closer, by 1 μm, to the semiconductor laser 61(a focal point of the optical system is brought away, by 1 μm, from thesemiconductor laser 61).

Subsequently, the i-MLSE detecting section 141 checks whether or not thei-MLSE detecting section 141 has detected an i-MLSE value apredetermined number of times (e.g., eight times) or more (process S12).Note that the predetermined number of times refers to a value that thecontrol section 14 has set in advance, as the number of processes to berepeated for detecting an i-MLSE value, within a range of sphericalaberration correcting values which are usable in the reproducing device100.

In a case where the i-MLSE detecting section 141 has detected an i-MLSEvalue less than the predetermined number of times (NO in process S12),the i-MLSE detecting section 141 provides an instruction to thespherical aberration correcting section 142. In response to theinstruction, the spherical aberration correcting section 142 (i) changesthe spherical aberration correcting value and (ii) controls the opticalsystem drive mechanism 651 (process S13). The spherical aberrationcorrecting section 142 then stores, in the memory 15, the sphericalaberration correcting value thus changed.

Note that the spherical aberration correcting value can be changed inaccordance with a given routine. The following description discusses, asan example, a case where the range of the spherical aberrationcorrecting values, which are usable in the reproducing device 100, isnot less than −4 μm and not less than 3 μm.

In a case where an initial setting value of the spherical aberrationcorrecting value is set to −4 μm, it is preferable to increase thespherical aberration correcting value by 1 μm (i.e., from −4 μm to −3μm, . . . , from 1 μm to 2 μm, from 2 μm to 3 μm) every time an i-MLSEvalue is detected. Meanwhile, in a case where the initial setting valueof the spherical aberration correcting value is set to 3 μm, it ispossible to reduce the spherical aberration correcting value by 1 μm(i.e., from 3 μm to 2 μm, . . . , from −2 μm to −3 μm, from −3 μm to −4μm) every time an i-MLSE value is detected. This causes the i-MLSEdetecting section 141 to detect, as a result of carrying out thedetection the predetermined number of times (eight times), a pluralityof i-MLSE values within the range of the spherical aberration correctingvalues which are usable in the reproducing device 100.

Note that the initial setting value of the spherical aberrationcorrecting value is stored in advance in the memory 15. In accordancewith specifications of the reproducing device 100 and the optical disk1, (i) the initial setting value of the spherical aberration correctingvalue and (ii) a range within which the spherical aberration correctingvalue can fall are preferably set as appropriate. The processes S11through S13 described above are repeated until the i-MLSE detectingsection 141 detects i-MLSE values the predetermined number of times ormore. This causes i-MLSE values for respective spherical aberrationcorrecting values to be stored in the memory 15.

In a case where the i-MLSE detecting section 141 detects i-MLSE valuesthe predetermined number of times or more (YES in process S12), thei-MLSE detecting section 141 compares all of the i-MLSE values thusdetected with each other (process S14). The i-MLSE detecting section 141then identifies a minimum i-MLSE value (process S15).

The i-MLSE detecting section 141 (i) reads out, from the memory 15, aspherical aberration correcting value corresponding to the minimumi-MLSE value and (ii) determines a spherical aberration correcting valueto be used to reproduce information (process S16). Upon receipt of aninstruction from the i-MLSE detecting section 141, the sphericalaberration correcting section 142 controls, in accordance with thespherical aberration correcting value, the optical system drivemechanism 651 to correct a spherical aberration (spherical aberrationcorrecting step).

In the processes S1 through S6 and the processes S11 through S16 (signalquality evaluating step), the i-MLSE detecting section 141 (i) detectsi-MLSE values and (ii) evaluates quality of a reproduction signal. Thisallows the reproducing device 100 to reproduce the optical disk 1 byusing a spherical aberration correcting value at which the i-MLSE valuebecomes minimum.

Embodiment 1 describes an example arrangement in which the i-MLSEdetecting section 141 and the spherical aberration correcting section142 are provided in the control section 14. Note, however, that thearrangements of the i-MLSE detecting section 141 and the sphericalaberration correcting section 142 are not limited to this.Alternatively, the i-MLSE detecting section 141 and the sphericalaberration correcting section 142 can be provided outside of the controlsection 14 so as to operate in conjunction with the control section 14.

<Configuration of Optical Disk>

The inventors of the present application carried out experiments fordemonstrating an effect of Embodiment 1, with respect to two types ofoptical disks A and B each having a configuration similar to that of theoptical disk 1. Prior to descriptions of the experiments, the followingdescription discusses a configuration of the optical disk 1 withreference to FIGS. 4 and 5.

FIG. 4 is a cross sectional view illustrating an optical disk 1. Theoptical disk 1 is configured such that an information recording layer(functional layer) 3 and a light transmitting layer 4 are stacked on thesubstrate 2 in this order. In other words, the light transmitting layer4, the information recording layer 3, and the substrate 2 are providedin this order in the optical disk 1, reproduction light being incidenton the light transmitting layer 4. The optical disk 1 is asuper-resolution medium including a mark (recording mark) or a spaceeach being shorter than an optical system resolution limit.

The substrate 2 is made of polycarbonate. A pit group is provided on asurface (information recording surface) of the substrate 2, on whichsurface the information recording layer 3 is provided. In the pit group,concavity and/or convexity each having a shape which varies dependinginformation to be recorded.

The information recording layer 3 is a layer (thin film) (i) in whichinformation is recorded and (ii) which is provided along the concavityand/or the convexity of the information recording surface of thesubstrate 2. The information recording layer 3 is a functional layerwhich enables super-resolution reproduction. The information recordinglayer 3 is a layer in which information is recorded. Recordedinformation is reproduced based on light which reflected off the layer.Specifically, the information recording layer 3 is a Ta thin film layerhaving a thickness of 12 nm.

The light transmitting layer 4 is made of ultraviolet cured resin (arefractive index is 1.50 for a reproduction light whose wavelength λ is405 nm) having a thickness of 100 μm. The light transmitting layer 4 (i)has a surface via which reproduction light enters and (ii) protectsinformation recording surfaces of the information recording layer 3 andthe substrate 2.

FIG. 5 is a plan view illustrating pits provided on the substrate 2 ofthe optical disk 1. In accordance with, for example, a (1,7) RLL (RunLength Limited) modulation method, information is recorded, on theoptical disk 1, in a form of marks and spaces having a plurality oflengths (D2T through D8T).

Note that the pits provided on the optical disk 1 indicate respectivemarks, and a gap between the respective pits provided along a trackindicates a space. The marks and spaces having a plurality of lengthsare provided so that an average length of a minimum mark length (D2T)and a minimum space length is 112 nm, in a scanning direction of thereproducing device 100. Note that the average length is shorter than anoptical system resolution limit (119 nm). In this case, the minimum marklength and the minimum space length are each D2T.

Note that a track pitch TpD of pits of the optical disk 1 is 0.32 μmwhich is identical with a standard BD (Blu-ray (registered trademark)disc)-ROM. According to the optical disk 1, the minimum mark length (112nm) is shorter than a minimum mark length (149 nm) of the standardBD-ROM (25 GB on a φ120 mm disk (non-super-resolution medium)). Thisallows information to be recorded on the optical disk 1 at a highdensity. It is therefore possible that the optical disk 1 recordsinformation of approximately 33.3 GB on a φ120 mm disk.

Note that information recorded on an optical disk 1 can contain, asaddress information, information indicative of a reproduction position.A process to be carried out for such an optical disk will be laterdescribed in Embodiment 2.

The configuration of the optical disk 1 described above is merelyillustrative. An alternative optical disk 1 can therefore include aplurality of information recording layers 3. Thicknesses of therespective layers of such an alternative optical disk 1 can be alteredas appropriate in accordance with, for example, the number of layers tobe provided.

<Experiment for Demonstration>

The inventors of the present application carried out experiments fordemonstration by carrying out Experiment 1 and Experiment 2 with respectto each of optical disks A and B. Note that the optical disks A and Beach have a configuration similar to that of the optical disk 1described in FIG. 4, except for cutting conditions for forming pits.That is, the optical disk A differs, in shapes of pits, from the opticaldisk B.

(Experiment 1) An i-MLSE of each of the optical disks A and B wasmeasured while changing a spherical aberration correcting value.

That is, Experiment 1 was carried out by use of (i) a BD evaluationsystem (DDU-1000 (manufactured by Pulstec Industrial Co.,Ltd.)/reproducing optical system: reproduction light wavelength (λ) 405nm, numerical aperture (NA) 0.85) and (ii) a BD evaluation signaldetector (SD3) manufactured by Pulstec Industrial Co., Ltd. By use ofthe BD evaluation system and the BD evaluation signal detector, (i) areproduction power and a reproduction speed were fixed to 1.0 mW and7.38 m/s, respectively and (ii) a set value for spherical aberrationcorrecting (i.e., an initial value of the spherical aberrationcorrecting value) which set value corresponds to 100 μm, which is thethickness of the light transmitting layer, was set to 0 μm. An i-MLSEwas then measured by changing the spherical aberration correcting value.

(Experiment 2) Amplitudes of RF signals of the respective optical disksA and B were measured while changing the spherical aberration correctingvalue. Experiment 2 was carried out by use of the devices and theexperimental conditions which are similar to those used in Experiment 1.

<Result of Experiments for Demonstration>

The following description discusses, with reference to (a) and (b) ofFIG. 6, results of the experiments for demonstration which have beencarried out with respect to the optical disks A and B.

(b) of FIG. 6 is a graph showing (i) a relationship between thespherical aberration correcting value and the i-MLSE and (ii) arelationship between the spherical aberration correcting value and theamplitude of the RF signal, which relationships were obtained as resultsof the experiments for demonstration which have been carried out withrespect to the optical disk B. In (b) of FIG. 6, a spherical aberrationcorrecting value obtained when the i-MLSE becomes minimum coincides witha spherical aberration correcting value obtained when the amplitude ofthe RF signal becomes maximum.

As shown in (b) of FIG. 6, even in a case of a read-only optical disk(i.e., the optical disk B, which is a super-resolution medium) in whichinformation is recorded in a form of a pit group which includes one ormore pits shorter than an optical system resolution limit, it is oftenthe case that spherical aberration correcting values (new referencecorrection value) obtained when an i-MLSE becomes minimum (i.e., signalquality is best) coincides with a spherical aberration correcting value(conventional reference correcting value) obtained when an amplitude ofan RF signal becomes maximum. Such a coincidence is similar to aread-only optical disk (i.e., a conventional optical disk which is anon-super-resolution medium) in which information is recorded in a formof a pit group including only pits longer than the optical systemresolution limit.

Note that the super-resolution medium refers to an optical informationrecording medium in which information is reproduced by asuper-resolution technique. Meanwhile, the non-super-resolution mediumrefers to a non-super-resolution region in which information isreproduced without using the super-resolution technique (i.e., in whichinformation is unreproducible by the super-resolution technique).

Meanwhile, (a) of FIG. 6 is a graph showing (i) a relationship betweenthe spherical aberration correcting value and the i-MLSE and (ii) arelationship between the spherical aberration correcting value and theamplitude of the RF signal, which relationships were obtained as resultsof the experiments for demonstration which have been carried out withrespect to the optical disk A. In (a) of FIG. 6, a spherical aberrationcorrecting value obtained when the i-MLSE becomes minimum does notcoincide with a spherical aberration correcting value obtained when theamplitude of the RF signal becomes maximum.

As shown in (a) of FIG. 6, in a case of a read-only optical disk (i.e.,the optical disk A, which is a super-resolution medium) in whichinformation is recorded in a form of a pit group which includes one ormore pits shorter than an optical system resolution limit, it sometimeshappens that a spherical aberration correcting value obtained when ani-MLSE becomes minimum (i.e., signal quality is best) greatly differs,depending on shapes of pits, from a spherical aberration correctingvalue obtained when an amplitude of an RF signal becomes maximum.

<Effect>

In general, reliability of an optical disk reproducing system(reproducing device) is damaged in a case where i-MLSE>15.5% Note,however, that the i-MLSE value of the optical disk A becomesapproximately 18% in a case of a spherical aberration correcting valueobtained when the amplitude of the RF signal becomes maximum.

Consequentially, in a case of a conventional reproducing device whichdetermines a spherical aberration correcting value based on an amplitudeof an RF signal, it sometimes happens that information reproduction withhigh reliability will not be carried out with respect to asuper-resolution medium (e.g., the optical disk A). That is, itsometimes happens that the conventional reproducing device will notcarry out information reproduction with inherent signal quality of thesuper-resolution medium.

In contrast, the reproducing device 100 of Embodiment 1 determines aspherical aberration correcting value based on an index (i.e., i-MLSEvalue), itself, indicative of signal quality. Specifically, in a casewhere the reproducing device 100 reproduces the optical disk A, ani-MLSE value becomes approximately 14%. In a case where the reproducingdevice 100 reproduces the optical disk B, an i-MLSE value becomesapproximately 10%.

That is, the reproducing device 100 makes it possible to carry outinformation reproduction with inherent signal quality of the opticaldisk 1 which is the super-resolution medium. This brings about an effectof increasing reliability of each reproduction of the optical disks Aand B.

More specifically, the reproducing device 100 includes the i-MLSEdetecting section 141 and the spherical aberration correcting section142. The i-MLSE detecting section 141 evaluates quality of areproduction signal which has been converted by the RF signal processingcircuit 9. The spherical aberration correcting section 142 corrects aspherical aberration caused by the optical pickup 6, by use of a resultof evaluation of the quality (i.e., i-MLSE value) of the reproductionsignal which quality has been evaluated by the i-MLSE detecting section141.

Unlike the reproducing device 100 of Embodiment 1, the conventionalreproducing device has reproduced the optical disk 1 by using not thespherical aberration correcting value obtained when the i-MLSE valuebecomes minimum but the spherical aberration correcting value obtainedwhen the amplitude (reflectance) of the RF signal becomes maximum. Thatis, the conventional reproducing device (i) has changed the sphericalaberration correcting value by use of an RF signal amplitude detectorwhich is also used during a layer jump to each layer and (ii) hasselected, as a spherical aberration correcting value to be used toreproduce information, the spherical aberration correcting valueobtained when the amplitude of the RF signal becomes maximum.

This is because (i) a person skilled in the art has recognized as commonknowledge that, in a signal characteristic of a reproduction signal,return light, caused by the reflectance of the optical informationrecording medium, is proportional to an amount of light which isreceived by the reproducing device and (ii) spherical aberrationcorrections made by other methods causes an increase in cost. As hasbeen described, however, it becomes clear that reproduction of asuper-resolution medium will never be carried out with inherent signalquality of the super-resolution medium, depending on shapes of pits ofthe super-resolution medium.

Unlike a conventional case where the spherical aberration is correctedby use of the amplitude of the RF signal, since the reproducing device100 includes the i-MLSE detecting section 141 and the sphericalaberration correcting section 142, it is capable of accuratelyreproducing information, such as content, recorded on unspecified numberof super-resolution media.

The reproducing device 100 of Embodiment 1 brings about a further effectof determining a suitable spherical aberration correcting value in asmaller reproduction range (i.e., smaller population parameter) of theoptical disk 1, as compared with a reproducing device 200 of Embodiment2 (later described).

Alternatively, it is conceivable to employ a configuration in which ajitter value is used as an index indicative of the signal quality. In acase where jitter is detected, however, it is impossible to correctlyevaluate signal quality of a pit group which includes one or more pitsshorter than an optical system resolution limit. This requires manyadditional components (functions) in order to determine a suitablespherical aberration correcting value.

In contrast, since the reproducing device 100 uses the i-MLSE value asthe index indicative of the signal quality, it has an advantage in thatcomponents and cost are reduced, as compared with the arrangement inwhich a jitter value is used as the index indicative of the signalquality.

Embodiment 2

The following description discusses another embodiment of the presentinvention with reference to FIG. 7. Note that, for convenience, memberswhich have functions identical to those of Embodiment 1 are givenidentical reference numerals, and are not described repeatedly.

<Configuration of Reproducing Device>

FIG. 7 is a functional block diagram schematically illustrating aconfiguration of the reproducing device 200 of Embodiment 2. Thereproducing device 200 of Embodiment 2 has a configuration obtained byreplacing, with a control section 24, the control section 14 of thereproducing device 100 of Embodiment 1. Note that other members of thereproducing device 200 of Embodiment 2 are identical to those of thereproducing device 100 of Embodiment 1. Such members are thus givenidentical reference numerals, and are not described repeatedly.

The control section 24 includes an error rate detecting section 241(signal quality evaluating section, address information error detectingsection) and a spherical aberration correcting section 142. The controlsection 24 of Embodiment 2 is obtained by replacing, with the error ratedetecting section 241, the i-MLSE detecting section 141 of the controlsection 14 of Embodiment 1.

An RF signal processing circuit 9 supplies a reproduction signal to theerror rate detecting section 241. The error rate detecting section 241then extracts, from the reproduction signal, address information (known)indicative of a reproduction position.

The error rate detecting section 241 detects an error rate from theaddress information. The error rate detecting section 241 calculates,for example, a bit error rate (bER) based on the address information soas to detect the bER as the error rate.

The bER is indicative of a ratio of the number of error bits Ne to thetotal number of decoding bits Nt, which error bits Ne are contained in aresult obtained by decoding a reproduction signal which is obtained whena pit recorded on the optical disk 1 is reproduced. The bER isrepresented as bER=Ne/Nt.

Note that information to be used by the error rate detecting section 241is not limited to the address information, provided that the informationis known information.

As with the processes S11 through S16 earlier described, the error ratedetecting section 241 determines a spherical aberration correcting valueobtained when the error rate (result of evaluation of quality) becomesminimum. The reproducing device 200 starts information reproduction ofthe optical disk 1 as with the process S6.

<Effect>

The reproducing device 200 includes the error rate detecting section 241which evaluates quality of the reproduction signal by detecting an errorrate of address information contained in a reproduction signal. Thisallows the reproducing device 200 to determine a spherical aberrationcorrecting value based on the error rate. That is, the reproducingdevice 200 uses the error rate as an index indicative of signal quality.

As with the reproducing device 100 (the configuration which uses thei-MLSE value as the index indicative of the signal quality) ofEmbodiment 1, the reproducing device 200 of Embodiment 2 therefore makesit possible to carry out information reproduction with the inherentsignal quality of the optical disk 1 which is a super-resolution medium.This brings about an effect of increasing reliability of eachreproduction of the optical disks A and B. That is, it is possible toaccurately reproduce information, such as content, recorded onunspecified number of super-resolution media.

It is necessary to specify a standard reproduction position of theoptical disk 1 (i.e., a position, to be reproduced, out of positions atwhich user data, such as content, is recorded). A reproducing devicetherefore normally has a function of detecting an address from areproduced RF signal (reproduction signal supplied from the RF signalprocessing circuit 9).

Accordingly, the reproducing device 200 brings about an effect ofdetermining a suitable spherical aberration correcting value, withoutadding, to the reproducing device 200, a new function for detecting theindex indicative of the signal quality.

Note that, since the reproducing device 200 has a difficulty incalculating a bER based on content information, it is impossible to use,as the index indicative of the signal quality, the bER calculated basedon the content information. This is because address information of a ROMnormally contains no known information other than the addressinformation. It is therefore impossible to calculate a significant bERbased on the information in the ROM.

Embodiment 3

The following description discusses a further embodiment of the presentinvention with reference to FIGS. 8 through 11. Note that, forconvenience, members which have functions identical to those ofEmbodiments 1 and 2 are given identical reference numerals, and are notdescribed repeatedly.

<Configuration of Optical Disk>

FIG. 8 is a perspective view illustrating an external appearance of anoptical disk 20 to be reproduced by a reproducing device 300 ofEmbodiment 3. FIG. 9 is a plan view specifically illustrating a part aof the optical disk 20 illustrated in FIG. 8.

As illustrated in FIG. 8, according to the optical disk 20, a dataregion 22 (first region) and medium information regions 23 (secondregions) are provided in advance. In the data region 22, for example,information, such as content, is recorded, and in the medium informationregions 23, for example, information (i.e., medium information)regarding the optical disk 20 is recorded. That is, the optical disk 20differs from the optical disk 1 of Embodiment 1 in that the optical disk20 further includes the medium information regions 23.

Examples of the information regarding the optical disk 20 encompass (i)medium identification information indicating that the optical disk 20has the data region 22, (ii) reproduction speed information that thereproducing device 300 uses when reproducing the optical disk 20, (iii)a medium unique number for copy protection, and (iv) region positioninformation for specifying a position in the data region 22. Note thatthe medium identification information is not limited to a specific one,provided that it identifies (specifies) a type of medium of the opticaldisk 20. It is sufficient that at least the data region 22 indicates asuper-resolution recording region.

FIG. 9 is a view specifically illustrating the part a of the opticaldisk 20 illustrated in FIG. 8. As illustrated in FIG. 9, a plurality ofpits are arranged, at intervals of given track pitch TpD, in the dataregion 22 so that the plurality of pits form a line in a circumferentialdirection. Similarly, a plurality of pits are arranged, at intervals ofgiven track pitch TpR, in the medium information regions 23 so that theplurality of pits form a line in a circumferential direction.

A mark edge recording method, in which information is recordable by useof pits which vary in shape and size, is employed to record informationin each of the data region 22 and the medium information regions 23.Embodiment 3 employs a modulation recording method (recording encodingmethod), referred to as a 1-7PP (1-7 Parity Preserve/Prohibit RMTR(Repeated Minimum Transition Run Length)), which is a type of the markedge recording method. Specifically, pits are provided in each of thedata region 22 and the medium information regions 23 by a modulationmethod which is a type of a (1,7) RLL (Run Length Limited) modulation.For example, information is recorded by use of pits (or recording marks)of 2T through 8T. In Embodiment 3, for convenience, lengths of therespective pits in the data region 22 will be indicated by “D2T throughD8T” and lengths of the respective pits in the medium informationregions 23 will be indicated by “R2T through R8T” (see FIG. 9).

Note that the above modulation increases a recording density as follows.Specifically, (i) bit string pattern of original information(information which has not been subjected to the modulation) isconverted, without depending on the bit string pattern of the originalinformation, into a recording pattern having a given frequency bandwidth (i.e., combinations of recording marks and spaces whichcombinations are limited to several types combinations) and (ii) aminimal-length of the recording marks or of the spaces is increased soas to be longer than a minimal-length of recording marks or of spaces ofthe original information. In case of the 1-7PP modulation recordingmethod, a frequency band width is limited by (i) converting a 2-bit unitof the original information into a 3 channel bit and (ii) modulating arecording pattern into which the bit string pattern of the originalinformation has been converted so that lengths of recording marks and ofspaces are limited to lengths of 2 channel bit (2T) through 8 channelbit (8T). This causes minimal-lengths of the recording marks and of thespaces to become 1.5 times of those of the original information.Accordingly, the modulation by use of the 1-7PP modulation recordingmethod is suitable for high density recording. Note that the modulationmethod to be employed is not limited to the 1-7PP modulation.Alternatively, it is possible to employ other modulation methods,suitable for high density recording, such as (i) (1,7) RLL modulationother than the 1-7PP modulation, (ii) 8/16 modulation, and (iii) (2,7)RLL modulation.

That is, a reason that information is recorded by using, for example,the (1,7) RLL modulation, in which information is recorded by use ofpits or recording marks varying in length, is that the recording densityis increased by recording information by use of pits or recording markswhich have identical lengths.

As illustrated in FIG. 8, the data region 22 is provided between themedium information regions 23. The content is recorded in the dataregion 22 by providing, in the data region 22, pits which includeconcavity and/or convexity when a substrate is formed. The pits eachhave a length of D2T through D8T shown in FIG. 9. The minimal pit lengthD2T is shorter than an optical system resolution limit of thereproducing device 300. The content is recorded so as to include a pitshorter than the optical system resolution limit of the reproducingdevice 300 (super-resolution recording). This allows the optical disk 20to record content at a higher recording density, as compared with aconventional medium.

As illustrated in FIG. 8, the medium information regions 23 are providedin advance in each of an innermost circumferential part of and anoutermost circumferential part of the optical disk 20. Informationregarding the super-resolution medium 1 is recorded in the mediuminformation regions 23 in a form of pits including concavity and/orconvexity. The pits each have a length of R2T through R8T (see FIG. 9).The minimal pit length R2T is not less than the optical systemresolution limit of the reproducing device 300 (normal recording). Toput it another way, (i) each of the pits, provided in the mediuminformation regions 23, is longer than the minimal pit in the dataregion 22 and (ii) a recording density of information in the mediuminformation regions 23 is lower than a recording density of informationin the data region 22.

The medium information regions 23 are provided in the innercircumferential part and the outer circumferential part of the opticaldisk 20. Note, however, that the arrangement of the medium informationregions 23 is not limited to this. Alternatively, the medium informationregions 23 can be provided either in the inner circumferential part ofor the outer circumferential part of the optical disk 20.

A cross-sectional configuration of the optical disk 20 is similar tothat of the optical disk 1 of Embodiment 1. In other words, the opticaldisk 1 has a configuration similar to that of the data region 22.Further, also in the optical disk 1, formation of pits and recording ofinformation do not need to be carried out by the (1,7) RLL modulation.Alternatively, it is possible to form the pits and record information onthe optical disk 1 by each one of the various modulation methodsdescribed above, other than the (1,7) RLL modulation.

As has been described, the data region 22 is a super-resolution regionin which (i) content is recorded in a form of a first pit groupincluding one or more pits shorter than the optical system resolutionlimit of the reproducing device 300 and (ii) information, such as thecontent, is reproduced by the super-resolution technique. Meanwhile, themedium information regions 23 are each a non-super-resolution region inwhich (i) the medium identification information is recorded in a form ofa second pit group including pits each having a length not less than theoptical system resolution limit of the reproducing device 300 and (ii)information is reproduced without using the super-resolution technique(i.e., information is unreproducible by the super-resolution technique).

In other words, the optical disk 20 (i) is a read-only optical disk inwhich content is recorded in a form of pit group including one or morepits shorter than the optical system resolution limit and (ii) is anoptical information recording medium in which information isreproducible by the so-called super-resolution technique.

Note that, due to the following reasons, the optical disk 20 ofEmbodiment 3 has the data region 22 and the medium information regions23 as described above.

It is generally preferable that each of a super-resolution medium and aconventional medium is reproducible by a single reproducing device. Thatis, an optical information recording medium is preferably compatiblewith an optical information recording medium for use in each one ofcorresponding reproducing devices (i.e., recorded information isreproducible by each one of corresponding reproducing devices).

Note, however, that reproduction (i.e., super-resolution reproduction)of information recorded in a form of a pit group which includes one ormore pits shorter than the optical system resolution limit requiresreproduction power higher than a light intensity (reproduction power) ofreproduction light with which a conventional medium is to be irradiated.Accordingly, in a case where the conventional medium is irradiated withreproduction light having reproduction power for the super-resolutionreproduction, the conventional medium may be damaged.

As such, a reproducing device capable of reproducing each of thesuper-resolution medium and the conventional medium is preferablyconfigured to (i) determine whether an optical information recordingmedium, which is subjected to a reproduction process, is asuper-resolution medium or a conventional medium and (ii) in a casewhere the reproducing device determines that the optical informationrecording medium is the super-resolution medium, irradiate, the opticalinformation recording medium with reproduction power for thesuper-resolution reproduction. That is, the reproducing devicepreferably increases a light intensity, from the reproduction power forthe conventional medium to the reproduction power for thesuper-resolution reproduction, only in a case where the reproducingdevice determines that the optical information recording medium is thesuper-resolution medium.

The optical disk 20 has the data region 22 and the medium informationregions 23 as described above. This allows the reproducing device, whichis configured as described above so as to be capable of reproducing eachof the super-resolution medium and the conventional medium, to irradiateeach of the data region 22 and the medium information regions 23 withreproduction light having a corresponding suitable light intensity. Thatis, the optical disk 20 can function as an optical information recordingmedium which is compatible with an optical information recording mediumfor use in the reproducing device.

Note that it is conceivable to cause the reproducing device to identifyan optical information recording medium as a super-resolution medium, byrecording medium identification information on the optical informationrecording medium in a form of a pit group including one or more pitsshorter than the optical system resolution limit so that the mediumidentification information is not reproducible even by irradiating theoptical information recording medium with reproduction light havingreproduction power for a conventional medium.

Note, however, that the reproducing device may, in some cases, not beable to reproduce medium identification information due to, for example,stain adhered to a surface of the conventional medium. In such a case,the reproducing device determines that (i) the medium identificationinformation is not reproducible and (ii) an object to be reproduced is asuper-resolution medium, even when such an object is actually aconventional medium. As such, the reproducing device irradiates theconventional medium with reproduction light having reproduction powerfor use in a super-resolution reproduction. This may cause theconventional medium to be damaged.

In view of the circumstances, the medium identification information ispreferably provided in a form of a pit group including one or more pitsnot less than the optical system resolution limit, as has beendescribed.

<Configuration of Reproducing Device>

FIG. 10 is a functional block diagram schematically illustrating aconfiguration of the reproducing device 300 of Embodiment 3. Thereproducing device 300 of Embodiment 3 has a configuration obtained byreplacing, with a control section 34, the control section 14 of thereproducing device 100 of Embodiment 1. Note that other members of thereproducing device 300 of Embodiment 3 are identical to those of thereproducing device 100 of Embodiment 1. Such members are thus givenidentical reference numerals, and are not described repeatedly.

The control section 34 includes an i-MLSE detecting section 141, a firstspherical aberration correcting section 342, and a second sphericalaberration correcting section 343. The control section 34 of Embodiment3 can be obtained by (i) replacing the spherical aberration correctingsection 142 of the control section 14 in accordance with Embodiment 1with the first spherical aberration correcting section 342 and (ii)adding the second spherical aberration correcting section 343 to thecontrol section 14.

The first spherical aberration correcting section 342 is a membersimilar to the spherical aberration correcting section 142, and specificdescription on the first spherical aberration correcting section 342 istherefore omitted. The first spherical aberration correcting section 342corrects a spherical aberration by controlling an optical system drivemechanism 651 by using a spherical aberration correcting value obtainedwhen an i-MLSE value becomes minimum.

The second spherical aberration correcting section 343 is a membersimilar to a spherical aberration correcting section provided in theconventional reproducing device. The second spherical aberrationcorrecting section 343 corrects a spherical aberration by controllingthe optical system drive mechanism 651 by using a spherical aberrationcorrecting value obtained when an amplitude of an RF signal becomesmaximum.

The reproducing device 300 is a reproducing device for reproducing theoptical disk 20. The reproducing device 300 therefore needs to reproduceeach of the data region 22 and the medium information regions 23.

The reproducing device 300 therefore includes, as two sphericalaberration correcting sections, the first spherical aberrationcorrecting section 342 and the second spherical aberration correctingsection 343. The first spherical aberration correcting section 342serves as a spherical aberration correcting section for reproducing theinformation recorded in the data region 22. The second sphericalaberration correcting section 343 serves as a spherical aberrationcorrecting section for reproducing the information recorded in themedium information regions 23.

In other words, in a case where the first spherical aberrationcorrecting section 342 reproduces the information recorded in the dataregion 22, the first spherical aberration correcting section 342corrects a spherical aberration by using a result (i-MLSE value) ofevaluation of quality of a reproduction signal indicative of thecontent. In contrast, in a case where the second spherical aberrationcorrecting section 343 reproduces the information recorded in the mediuminformation regions 23, the second spherical aberration correctingsection 343 corrects a spherical aberration by carrying out a processdifferent from the first spherical aberration correcting.

In the data region 22, the information is recorded in a form of a pitgroup including one or more pits shorter than the optical systemresolution limit. Accordingly, as has been described in Embodiment 1,the reproducing device 300 includes the first spherical aberrationcorrecting section 342 for correcting a spherical aberration caused byvariation in thickness of a light transmitting layer 4 of the opticaldisk 20 (super-resolution medium).

In contrast, in the medium information regions 23, the information isrecorded in a form of a pit group including one or more pits not lessthan the optical system resolution limit. Accordingly, the firstspherical aberration correcting section 342, which corrects thespherical aberration caused by variation in thickness of the lighttransmitting layer 4 of the optical disk 20, is not required. This isbecause, in a case where the first spherical aberration correctingsection 342 corrects the spherical aberration during recording theinformation in the medium information regions 23 is reproduced, adifference between respective i-MLSE values which correspond torespective spherical aberration correcting values become smaller, andthis may give rise to a difficulty in proper optimization of thespherical aberration. Furthermore, in a case where the error ratedetecting section corrects the spherical aberration during thereproduction of the information in the medium information regions 23, ittakes a good amount of time to optimize the spherical aberration. Inview of the circumstances, it is preferable to correct the sphericalaberration by use of the second spherical aberration correcting section343 which is a member similar to the spherical aberration correctingsection provided in the conventional reproducing device.

<Process of Reproducing Device>

FIG. 11 is a flow chart showing an example flow of how a reproductionoperation is carried out (control method and reproduction method), withrespect to the optical disk 20, in the reproducing device 300.

First, the reproducing device 300 is loaded with the optical disk20(process S21). The control section 34 of the reproducing device 300recognizes, via a sensor (not illustrated) provided in the controlsection 34, that it has been loaded with the optical disk 20.

Subsequently, the control section 34 controls a spindle motor 7 torotate (process S22). This causes the optical disk 20 to be driven androtated under, for example, an operating condition in which, forexample, a linear velocity is constant or a number of revolutions isconstant. The control section 34 carries out various settings withrespect to the reproducing device 300 in accordance with initial settingvalues stored in a memory 15.

Subsequently, the control section 34 controls a focusing/tracking drivecircuit 10 to focus the objective lens 660 on the optical disk 20(process S23). The control section 34 then controls thefocusing/tracking drive circuit 10 to carry out tracking of theobjective lens 660 with respect to a given position in the mediuminformation regions 23 (process S24).

The second spherical aberration correcting section 343 corrects aspherical aberration in accordance with an amplitude (reflectance) of anRF signal, i.e., by using a spherical aberration correcting valueobtained when a value of the amplitude of the RF signal becomes maximum(process S25; second spherical aberration correcting step). In doing so,the control section 34 determines the spherical aberration correctingvalue obtained when the value of the amplitude of the RF signal becomesmaximum by carrying out processes similar to the processes S11 throughS16. That is, the control section 34 (i) detects values of amplitudes ofRF signals which values correspond to respective spherical aberrationcorrecting values and (ii) specifies a maximum value among all of thevalues of the amplitudes of RF signals thus detected.

After the second spherical aberration correcting section 343 hascorrected the spherical aberration by using the spherical aberrationcorrecting value obtained when the value of the amplitude of the RFsignal becomes maximum, the control section 34 carries out areproduction with respect to the medium information regions 23 so as toobtain the medium information recorded in the medium information regions23 (process S26). The control section 34 stores, in the memory 15, themedium information thus obtained.

Subsequently, the control section 34 controls the focusing/trackingdrive circuit 10 to release a state in which the tracking of theobjective lens 660 is being carried out with respect to a given position(process S27).

The control section 34 carries out the various settings with respect tothe reproducing device 300 by selecting the initial setting values ofthe optical disk 20 which initial setting values are stored in thememory 15. For example, the control section 34 analyzes mediumidentification information contained in obtained medium information soas to determine whether or not the optical disk 20 is a super-resolutionmedium or a conventional medium (non-super-resolution medium).Specifically, in a case where the control section 34 determines that theoptical disk 20 is a super-resolution medium, it changes an output of asemiconductor laser 61 from reproduction power for the conventionalmedium to reproduction power for the super-resolution reproduction. Thecontrol section 34 then controls the focusing/tracking drive circuit 10to carry out tracking of the objective lens 660 with respect to a givenposition in the data region 22 (process S28).

The first spherical aberration correcting section 342 corrects aspherical aberration based on an index indicative of signal quality(i-MLSE), i.e., by using a spherical aberration correcting valueobtained when an i-MLSE value, which has been evaluated by the i-MLSEdetecting section 141, becomes minimum (process S29; first sphericalaberration correcting step). Note that specific processes in the processS29 are similar to those of the processes S11 through S16.

After the first spherical aberration correcting section 342 hascorrected the spherical aberration by using the spherical aberrationcorrecting value obtained when the i-MLSE value becomes minimum, thecontrol section 34 starts reproducing the information recorded in thedata region 22 (process S30).

Note that, in the process S28, it is possible to change a reproductionspeed (linear velocity) together with the reproduction power. This isbecause it is preferable to transfer, at a higher rate, information(e.g., information on a video image having high image quality) which (i)is to be utilized in the super-resolution medium and (ii) is recorded ata higher density. It is therefore preferable to transfer suchinformation at a rate higher than that of the medium information regions23. The linear velocity is more preferably a linear velocity (e.g.,double-speed) at which information can be reproduced at a channel bitrate of n (n: an integer) times of a channel bit rate of the mediuminformation regions 23. This is because it is possible to simplify anadjustment of the linear velocity.

<Effect>

According to the reproducing device 300, it is possible to suitablycarry out a spherical aberration correcting with respect to each of thedata region 22 (super-resolution region) and the medium informationregions 23 (non-super-resolution regions). Accordingly, the reproducingdevice 300 brings about an effect of increasing reliability ofreproduction of the optical disk 20 including the data region 22 and themedium information regions 23.

Note that, as with Embodiment 1, Embodiment 3 shows an example in whichthe i-MLSE is used as an index indicative of signal quality.Accordingly, the reproducing device 300 includes the i-MLSE detectingsection 141.

Alternatively, as with Embodiment 2, it is possible to use an error rateas an index indicative of signal quality. In such a case, thereproducing device 300 can be configured to include the error ratedetecting section 241, instead of the i-MLSE detecting section 141.

Embodiment 4

The following description discusses still a further embodiment of thepresent invention with reference to FIG. 12. Note that, for convenience,members which have functions identical to those of Embodiments 1 through3 are given identical reference numerals, and are not describedrepeatedly.

<Configuration of Reproducing Device>

FIG. 12 is a functional block diagram schematically illustrating aconfiguration of a reproducing device 400 of Embodiment 4. Thereproducing device 400 of Embodiment 4 has a configuration obtained byreplacing, with a control section 44, the control section 34 of thereproducing device 300 of Embodiment 3. Note that other members of thereproducing device 400 of Embodiment 4 are identical to those of thereproducing device 300 of Embodiment 3. Such members are thus givenidentical reference numerals, and are not described repeatedly. As withEmbodiment 3, an optical disk to be reproduced by the reproducing device400 is the optical disk 20.

The control section 44 includes a difference adjusting section 441, afirst spherical aberration correcting section 342, and a secondspherical aberration correcting section 343. The control section 44 ofEmbodiment 4 has a configuration obtained by replacing the i-MLSEdetecting section 141 (or the error rate detecting section 241) with thedifference adjusting section 441.

An RF signal processing circuit 9 supplies a reproduction signal to thedifference adjusting section 441. The difference adjusting section 441extracts, from the reproduction signal, manufacturer information(information for specifying a manufacturer of the optical disk 20)contained in the medium identification information. Note that the mediumidentification information is recorded in the medium information regions23 of the optical disk 20. In order to reproduce the medium informationregions 23, the control section 44 (i) determines a spherical aberrationcorrecting value obtained when a value of an amplitude of an RF signalbecomes maximum and (ii) supplies the spherical aberration correctingvalue to the second spherical aberration correcting section 343.

The difference adjusting section 441 specifies a spherical aberrationcorrecting value (e.g., a spherical aberration correcting value which isrecommended by the manufacturer so that best signal quality is obtainedduring reproducing the data region 22) based on manufacturerinformation. The manufacturer information can be information containinga spherical aberration correcting value recommended by the manufacturer.Alternatively, the manufacturer information can be mere information byuse of which the manufacturer can be specified.

The following description assumes that (i) R1 represents a sphericalaberration correcting value (e.g., a spherical aberration correctingvalue recommended by each manufacturer of the optical disk 20) (i.e.,first spherical aberration correcting value) specified based on themanufacturer information and (ii) R2 indicates a spherical aberrationcorrecting value (i.e., second spherical aberration correcting value)obtained when an amplitude of an RF signal becomes maximum, which R1 andR2 are specified by each of the plurality of manufacturers of theoptical disk 20. The values R1 and R2 are stored in the memory 15 so asto be associated with each of manufacturer identifiers indicative of therespective plurality of manufacturers. The control section 44 controlsthe spherical aberration correcting value to be changed so that theamplitude of the RF signal becomes maximum. Note that it is hereinassumed that RP indicates a current spherical aberration correctingvalue which is set by the control section 44.

The plurality of manufacturers of the optical disk 20 store in advance,in the memory 15, (i) R1, which has been specified by using the resultof the evaluation of the quality of the reproduction signal indicativeof the content recorded in the data region 22 and (ii) R2, which hasbeen specified by using the amplitude of the reproduction signalindicative of the manufacturer information recorded in the mediuminformation regions 23, so that R1 and R2 are associated with eachmanufacturer.

During reproduction of the data region 22, the difference adjustingsection 441 calculates, by using the values R1 and R2, a difference ΔRbetween the spherical aberration correcting values, which ΔR is obtainedby ΔR=R1−R2. The values R1 and R2 are stored in the memory 15 so as tobe associated with each manufacturer (manufacturer identifier) indicatedby the manufacturer information which has been read out from the mediuminformation regions 23. The difference adjusting section 441 thensupplies, to the first spherical aberration correcting section 342, aspherical aberration correcting value (a spherical aberration correctingvalue to be used during reproducing of the content) R, which is obtainedby R=RP+ΔR, i.e., by adding the difference ΔR to the current sphericalaberration correcting value RP.

Note that the memory 15 can store therein, in advance, together with thevalues R1 and R2, difference information indicative of the difference ΔRso that the difference information is associated with each of themanufacturer identifiers. The values R1 and R2 are not necessarilystored in the memory 15. In such a case, the difference adjustingsection 441 can (i) read out the difference ΔR from the memory 15 so asto calculate the spherical aberration correcting value R and (ii)supply, to the first spherical aberration correcting section 342, thespherical aberration correcting value R thus calculated.

<Effect>

In a case of producing an optical disk, manufacturing conditions, suchas a cutting condition for forming pits, vary depending on amanufacturer of the optical disk. Accordingly, shapes of the pits of theoptical disk may also vary depending on the manufacturer of the opticaldisk. A difference between (i) the spherical aberration correcting valueobtained when the signal quality becomes best and (ii) the sphericalaberration correcting value obtained when the amplitude of the RF signalbecomes maximum, depends on the manufacturer of the optical disk.

According to the reproducing device 400, a difference, which is usedduring reproducing the data region 22, between (i) the sphericalaberration correcting value (R1) which is specified based on themanufacturer information and (ii) the spherical aberration correctingvalue (R2) which is obtained when the amplitude of the RF signal becomesmaximum, is specified in advance as the difference ΔR for eachmanufacturer of the optical disk.

Upon receipt of the spherical aberration correcting value R=RP+ΔR fromthe difference adjusting section 441, the first spherical aberrationcorrecting section 342 corrects a spherical aberration caused duringreproducing the data region 22. This allows the reproducing device 400to reproduce the data region 22 by using a suitable spherical aberrationcorrecting value varied depending on each manufacturer of the opticaldisk.

R1 is, for example, a representative value of spherical aberrationcorrecting values recommended by each manufacturer of an optical disk.Accordingly, even in a case where an optical disk is manufactured by asame manufacturer, a spherical aberration correcting value which is mostsuitable for reproducing a data region 22 of the optical disk issometimes not coincide with the above R1 due to a manufacturingtolerance of the optical disk and the like.

The reproducing device 400 (i) specifies, during reproducing of themedium information regions 23, the spherical aberration correcting valueRP with respect to the optical disk 20 and then (ii) reproduces the dataregion 22 by using the spherical aberration correcting valueR=RP+ΔR=R1+(PR−R2). Accordingly, the spherical aberration correctingvalue R to be used in the reproducing device 400 (i) has individuallybeen set for the optical disk 20 and (ii) is a spherical aberrationcorrecting value more suitable for reproducing the data region 22, ascompared with the representative value R1.

The reproducing device 400 obtains manufacturer information so as todetermine a spherical aberration correcting value to be used duringreproducing the data region 22, instead of detecting an i-MLSE (or anerror rate of address information) based on which signal quality isevaluated. This eliminates the necessity of including the i-MLSEdetecting section 141 (or the error rate detecting section 241) in thereproducing device 400. As such, it is only necessary to include thedifference adjusting section 441 which has a function simpler than thei-MLSE detecting section 141 (or the error rate detecting section 241).

This allows the reproducing device 400 of Embodiment 4 to bring about aneffect of providing a lower-cost reproducing device, as compared withthe reproducing devices of Embodiments 1 through 3.

Embodiment 4 discusses an example case where the spherical aberrationcorrecting value, recommended by the manufacturer of the optical disk20, is used as the value R1 stored in the memory 15. Note, however, thatit is also assumed that there exists a manufacturer that does notprovide a recommended value for the spherical aberration correctingvalue. In this case, it is preferable for a user to (i) specify a valueR1 in advance and (ii) store, in the memory 15, the value R1 so that thevalue R1 is associated with the each of the manufacturer identifiers.

For example, in a case of using the reproducing device 300 of Embodiment3, a spherical aberration correcting value, which is obtained when thei-MLSE value becomes minimum, is specified as a spherical aberrationcorrecting value suitable for reproducing the data region 22. A useronly needs to store, in the memory 15 of the reproducing device 400, thespherical aberration correcting value as the value R1.

This allows the reproducing device 400 to reproduce the optical disk 20,even in a case where the manufacturer does not provide the recommendedvalue for the spherical aberration correcting value.

Embodiment 5

The following description discusses yet another embodiment of thepresent invention with reference to FIGS. 13 through 16. Note that, forconvenience, members which have functions identical to those ofEmbodiments 1 through 4 are given identical reference numerals, and arenot described repeatedly.

<Configuration of Optical Disk>

FIG. 13 is a perspective view illustrating an external appearance of anoptical disk 30 to be reproduced by a reproducing device 500 ofEmbodiment 5. FIG. 14 is a view schematically illustrating an example ofstripes to be formed in a BCA (Burst Cutting Area) recording region 39of the optical disk 30 illustrated in FIG. 13.

The optical disk 30 has the BCA recording region 39, a mediuminformation region 33, a data region 32, a medium information region 33in this order from an inner circumferential side of the optical disk 30.The data region 32 and the medium information regions 33 haveconfigurations identical to those of the data region 22 and the mediuminformation regions 23, respectively, and are not described repeatedly.That is, the optical disk 30 differs from the optical disk 20 ofEmbodiment 3 in that the optical disk 30 has the BCA recording region 39on an innermost circumferential side of the optical disk 30.

As illustrated in FIG. 13, the BCA recording region 39 is a region inwhich information (i.e., equivalent to the information regarding theoptical disk 20 of Embodiment 3) (medium information) regarding theoptical disk 30 is recorded, and the information includes mediumidentification information. The medium information is recorded in thefollowing manner. That is, an information recording layer is irradiatedwith pulse laser light emitted from a YAG (Yttrium Aluminum Garnet)laser or the like. This causes stripes (barcodes) to be formed, eachhaving (i) a width w of approximately 10 μm and (ii) a length l ofapproximately several hundreds of μm (see FIG. 14). That is, in the BCArecording region 39, the medium identification information is recordedin a stripe shape.

The stripes formed in the BCA recording region 39 are thus each largerthan, for example, a pit having a length of approximately severalhundreds of nm. This allows the reproducing device 500 to reproduce themedium information without carrying out tracking, even in a case wherefocusing on the BCA recording region 39 is slightly shifted. That is,while the reproducing device 500 is reproducing the medium information,the reproducing device 500 can reproduce the medium information withoutcorrecting (optimizing) a spherical aberration.

In a case where the optical disk 30 is made up of a plurality of layers,the BCA recording region 39 is provided on the information recordinglayer which is provided immediately above a substrate which is arrangedfarthest from a side from which reproduction light enters. Note,however, that the arrangement of the BCA recording region 39 is notlimited to this.

The optical disk 30 only needs to be provided with at least the BCArecording region 39 and the data region 32.

<Configuration of Reproducing Device>

FIG. 15 is a functional block diagram schematically illustrating aconfiguration of the reproducing device 500 of Embodiment 5. Thereproducing device 500 of Embodiment 5 is a reproducing device forreproducing the optical disk 30. The reproducing device 500 ofEmbodiment 5 has a configuration obtained by replacing, with a controlsection 54, the control section 14 of the reproducing device 100 ofEmbodiment 1. Note that other members of the reproducing device 500 ofEmbodiment 5 are identical to those of the reproducing device 100 ofEmbodiment 1. Such members are thus given identical reference numerals,and are not described repeatedly.

The control section 54 includes an i-MLSE detecting section 141, aspherical aberration correcting section 142, and a BCA reproductioncontrol section 543. The control section 54 of Embodiment 5 has aconfiguration obtained by adding the BCA reproduction control section543 to the control section 14 of Embodiment 1.

Note that the spherical aberration correcting section 142 of Embodiment5 has a function similar to that of the first spherical aberrationcorrecting section 342 in which, during reproduction of content recordedin the data region 22, a spherical aberration is corrected by using aresult of evaluated quality of a reproduction signal indicative of thecontent. Note also that, in a case where the medium information recordedin the BCA recording region 39 is reproduced, the spherical aberrationcorrecting section 142 corrects a spherical aberration by using aninitial value of a spherical aberration correcting value. That is, thespherical aberration to be corrected during reproduction of the mediuminformation is not corrected based on an amplitude of an RF signal.

The BCA reproduction control section 543 controls a focusing/trackingdrive circuit 10 to cause each section of an optical pickup 6 to carryout an operation for reproducing the medium information recorded in theBCA recording region 39.

<Process of Reproducing Device>

FIG. 16 is a flow chart showing an example flow of how a reproductionoperation is carried out (control method and reproduction method), withrespect to the optical disk 30, in the reproducing device 500.

First, the reproducing device 500 is loaded with the optical disk30(process S41). The control section 54 of the reproducing device 500recognizes, by use of a sensor (not illustrated) provided in the controlsection 54, that it has been loaded with the optical disk 30.

Subsequently, the control section 54 controls a spindle motor 7 torotate (process S42). This causes the optical disk 30 to be driven androtated under, for example, an operating condition in which, forexample, a linear velocity is constant or a number of revolutions isconstant.

Subsequently, the BCA reproduction control section 543 controls thefocusing/tracking drive circuit 10 to move the optical pickup 6 to agiven position in the BCA recording region 39. The BCA reproductioncontrol section 543 then controls an objective lens 660 to be focused onthe BCA recording region 39 (process S43).

After the spherical aberration correcting section 142 has corrected thespherical aberration by using an initial value of a spherical aberrationcorrecting value stored in a memory 15, the BCA reproduction controlsection 543 obtains medium information recorded in the BCA recordingregion 39 (process S44). Note that, in a case where the sphericalaberration correcting value has been already set to the initial value,the BCA reproduction control section 543 obtains the medium information,instead of correcting the spherical aberration. The control section 54stores, in the memory 15, the medium information thus obtained.

Note that, as has been described, no tracking is required duringobtaining the medium information from the BCA recording region 39.Accordingly, prior to the process S44, no tracking is carried out withrespect to the BCA recording region 39.

By using the medium information stored in the memory 15, the controlsection 54 selects initial setting values of the optical disk 30 so asto carry out various settings with respect to the reproducing device500, which initial setting values are stored in the memory 15. Forexample, as has been described in Embodiment 3, the control section 54(i) determines whether or not the optical disk 30 is a super-resolutionmedium and (ii) changes (a) an output of a semiconductor laser 61 and(b) a reproduction speed (linear velocity). The control section 54 thencontrols the focusing/tracking drive circuit 10 to carry out tracking ofthe objective lens 660 with respect to a given position in the dataregion 32 (process S45).

The spherical aberration correcting section 142 corrects a sphericalaberration based on an index indicative of signal quality (i-MLSE),i.e., by using a spherical aberration correcting value obtained when thei-MLSE value becomes minimum (process S46). Note that a specific processflow of the process S46 is similar to those of the processes S11 throughS16.

After the control section 54 controls the spherical aberrationcorrecting section 142 to correct the spherical aberration by using thespherical aberration correcting value obtained when the i-MLSE valuebecomes minimum, the control section 54 starts reproducing informationrecorded in the data region 32 (process S47).

<Effect>

With the reproducing device 500, it is possible to reproduce the opticaldisk 30, which has the BCA recording region 39 in addition to the dataregion 32 (super-resolution region).

The reproducing device 500 can reproduce the medium information recordedin the BCA recording region 39, without requiring to (i) carry outtracking with respect to the BCA recording region 39 and (ii) optimizethe spherical aberration correcting so as to carry out reproducing ofthe BCA recording region 39.

The reproducing device 500 of Embodiment 5 can bring about an effect ofstarting reproduction of the optical disk 30 in a time period shorterthan a time period which the reproducing device 300 of Embodiment 3needs in order to start reproduction of the optical disk 20.

[Software Implementation Example]

Control blocks of the reproducing devices 100 through 500 (particularly,the i-MLSE correcting section 141, the spherical aberration correctingsection 142, the error rate detecting section 241, the first sphericalaberration correcting section 342, the second spherical aberrationcorrecting section 343, the difference adjusting section 441, and theBCA reproduction control section 543) can be realized by a logic circuit(hardware) provided in an integrated circuit (IC chip) or the like orcan be alternatively realized by software as executed by a CPU (CentralProcessing Unit).

In the latter case, the reproducing devices 100 through 500 each includea CPU that executes instructions of a program that is software realizingthe foregoing functions; ROM (Read Only Memory) or a storage device(each referred to as “storage medium”) in which the program and variouskinds of data are stored so as to be readable by a computer (or a CPU);and RAM (Random Access Memory) in which the program is loaded. An objectof the present invention can be achieved by a computer (or a CPU)reading and executing the program stored in the storage medium. Examplesof the storage medium encompass “a non-transitory tangible medium” suchas a tape, a disk, a card, a semiconductor memory, and a programmablelogic circuit. The program can be supplied to the computer via anytransmission medium (such as a communication network or a broadcastwave) which allows the program to be transmitted. Note that the presentinvention can also be achieved in the form of a computer data signal inwhich the program is embodied via electronic transmission and which isembedded in a carrier wave.

[Main Points]

A reproducing device (100, 200, 300, 500) of a first aspect of thepresent application is a reproducing device capable of reproducingcontent from an optical information recording medium (optical disk 1) inwhich the content is recorded in a form of a pit group including one ormore pits shorter than an optical system resolution limit of thereproducing device, including: an irradiation section (optical pickup 6)for irradiating the optical information recording medium withreproduction light; a conversion section (RF signal processing circuit9) for converting, into reproduction signal (RF signal) indicative ofthe content, light which reflected off the optical information recordingmedium; a signal quality evaluating section (i-MLSE detecting section141, error rate detecting section 241) for evaluating quality of thereproduction signal converted by the conversion section; and a sphericalaberration correcting section (142) for correcting a sphericalaberration caused by the irradiation section, by using a result ofevaluation of the quality of the reproduction signal which quality hasbeen evaluated by the signal quality evaluating section.

In a case where a reproducing device reproduces an optical informationrecording medium (i.e., a non-super-resolution medium (i) in which noneof pits is shorter than an optical system resolution limit of thereproducing device and (ii) which cannot be reproduced by asuper-resolution technique) in which information is recorded in a formof a pit group including pits each having a length not less than theoptical system resolution limit of the reproducing device, a sphericalaberration is corrected based on an amplitude of an RF signal (seePatent Literature 1, for example). That is, a spherical aberrationcorrecting value for correcting the spherical aberration is determinedso that the amplitude of the RF signal becomes maximum, and thespherical aberration is corrected by using the spherical aberrationcorrecting value thus determined. According to the non-super-resolutionmedium, by correcting the spherical aberration so that the amplitude ofthe RF signal becomes maximum, it is possible to reproduce theinformation while a signal characteristic is high.

Examples of a reason that the amplitude of the RF signal is used tocorrect the spherical aberration during reproduction of thenon-super-resolution medium encompass the following reason. That is, itis common knowledge for a person skilled in the art that “a signalcharacteristic of a reproduction signal is proportional to an amount ofreturn light (reflected light amount, return light amount) which (i) iscaused by reflectance of an optical information recording medium(non-super-resolution medium) and (ii) is received by a reproducingdevice”. The reflectance refers to a ratio, to reproduction light, oflight which reflected off the optical information recording mediumirradiated with the reproduction light.

A function (member, section) for calculating the amplitude of the RFsignal is an essential configuration for the reproducing device toreproduce information recorded on an optical information recordingmedium made up of a plurality of layers. That is, another reason forusing the method described above is that a production cost increases ina case where a new function different from the function of calculatingthe amplitude of the RF signal is provided in the reproducing device soas to correct the spherical aberration.

Note, however, that, as described with reference to FIG. 6, theinventors of the present application found that, according to an opticalinformation recording medium (i.e., a super-resolution mediumreproducible by the super-resolution technique) in which content isrecorded in a form of a pit group including one or more pits shorterthan an optical system resolution limit of a reproducing device, asignal characteristic may be low, depending on shapes of pits providedon the super-resolution medium, even in a case where an amplitude of anRF signal becomes maximum. That is, it becomes therefore clear that, ina case where information recorded on a super-resolution medium isreproduced by a reproducing device which corrects a spherical aberrationbased on a light intensity of light which reflected off thesuper-resolution medium and received by the reproducing device,reproduction quality may deteriorate depending on the super-resolutionmedium.

In view of the circumstances, according to the aspect of the presentinvention, the signal quality evaluating section evaluates the qualityof the reproduction signal based on the light which reflected off theoptical information recording medium (super-resolution medium)irradiated with the reproduction light from the irradiation section. Thespherical aberration correcting section corrects the sphericalaberration caused by the irradiation section, by using the result of theevaluation of the quality of the reproduction signal which quality hasbeen evaluated by the signal quality evaluating section. With thearrangement, the spherical aberration correcting section corrects thespherical aberration by using the result of the evaluation of thequality of the reproduction signal, instead of using an amplitude of anRF signal.

Accordingly, during reproduction of the super-resolution medium, it ispossible to correct the spherical aberration while a signalcharacteristic is sufficiently high. This prevents a case where thespherical aberration is corrected while signal quality is low, whichcase occurs when the spherical aberration is corrected based on theamplitude of the RF signal.

With the aspect of the present invention, unlike a case where thespherical aberration is corrected by use of the amplitude of the RFsignal, it is therefore possible to accurately reproduce information,such as content, recorded on unspecified number of super-resolutionmedia.

A reproducing device (100, 200, 300, 500) of a second aspect of thepresent application is a reproducing device capable of reproducingcontent by irradiating, via an objective lens (600) having a numericalaperture of 0.85, an optical information recording medium withreproduction light having a wavelength of 405 nm, the opticalinformation recording medium (optical disk 1) including (a) a lighttransmitting layer (4) having a surface which the reproduction lightenters, (b) an information recording layer (3) which the reproductionlight reflects off so that information is reproduced, and (c) asubstrate (2) on which a pit group is provided in a scanning direction,the pit group including one or more pits shorter than 119 nm which is anoptical system resolution limit of the reproducing device, the lighttransmitting layer, the information recording layer, and the substratebeing provided in this order from a side from which the reproductionlight enters, the content being recorded in the information recordinglayer by use of the pit group, including: an irradiation section(optical pickup 6) for irradiating the optical information recordingmedium with reproduction light; a conversion section (RF signalprocessing circuit 9) for converting, into reproduction signalindicative of the content, light which reflected off the opticalinformation recording medium; a signal quality evaluating section(i-MLSE detecting section 141, error rate detecting section 241) forevaluating quality of the reproduction signal converted by theconversion section; and a spherical aberration correcting section(spherical aberration correcting section 142) for correcting a sphericalaberration caused by the irradiation section, by using a result ofevaluation of the quality of the reproduction signal which quality hasbeen evaluated by the signal quality evaluating section.

As described above, according to the non-super-resolution medium, bycorrecting the spherical aberration based on the amplitude of the RFsignal, it is possible to reproduce the information while the signalcharacteristic is high. Meanwhile, however, according to thesuper-resolution medium, it may not be possible to reproduce theinformation while the signal characteristic is high.

On the optical information recording medium which is to be reproduced bythe reproducing device of the aspect of the present invention, (i) thelight transmitting layer, the information recording layer, and thesubstrate are provided and (ii) the content is recorded in theinformation recording layer by providing, on the substrate, the pitgroup including one or more pits shorter than 119 nm, which is theoptical system resolution limit of the reproducing device. Thereproducing device of the aspect of the present invention irradiates,via the objective lens having a numerical aperture of 0.85, thereproduction light having a wavelength of 405 nm.

That is, the optical information recording medium to be reproduced bythe reproducing device of the aspect of the present invention is asuper-resolution medium and the reproducing device is capable ofreproducing content recorded on the super-resolution medium.

According to the aspect of the present invention, the signal qualityevaluating section evaluates the quality of the reproduction signalbased on the light which reflected off the optical information recordingmedium (super-resolution medium) irradiated with the reproduction lightirradiated from the irradiation section. The spherical aberrationcorrecting section corrects, by using the result of the evaluation ofthe quality of the reproduction signal which quality has been evaluatedby the signal quality evaluating section, the spherical aberrationcaused by the irradiation section.

As with the first aspect, unlike a case where the spherical aberrationis corrected by use of the amplitude of the RF signal, it is thereforepossible to accurately reproduce information, such as content, recordedon unspecified number of super-resolution media.

In a third aspect of the present invention, a reproducing device ispreferably arranged such that, in the first or second aspect of thepresent invention, the signal quality evaluating section is (i) ani-MLSE (Integrated-Maximum Likelihood Sequence Estimation) detectingsection (141) for (a) detecting an i-MLSE which is an evaluation indexfor evaluating a signal characteristic of the reproduction signal and(b) evaluating the quality of the reproduction signal or (ii) an addressinformation error detecting section (error rate detecting section 241)for (a) detecting an error rate of address information contained in thereproduction signal and (b) evaluating the quality of the reproductionsignal.

With the arrangement, the signal quality evaluating section is thei-MLSE detecting section or the address information error detectingsection.

In a case where the signal quality evaluating section is the i-MLSEdetecting section, the i-MLSE can be used as the result of theevaluation of the quality of the reproduction signal. Accordingly,during reproduction of a super-resolution medium, it is possible tocorrect a spherical aberration while a signal characteristic issufficiently high.

Meanwhile, in a case where the signal quality evaluating section is theaddress information error detecting section, the error rate of addressinformation can be used as the result of the evaluation of the qualityof the reproduction signal.

The address information error detecting section is normally provided ina reproduction device by which a super-resolution medium is to bereproduced. Accordingly, without providing, in the reproducing device, anew function (member, section) for evaluating quality of a reproductionsignal, it is possible to correct the spherical aberration duringreproduction of the super-resolution medium, by using the error rate ofthe address information which error rate has been detected by theaddress information error detecting section, while a signalcharacteristic is sufficiently high.

Note that, as described above, the inventors of the present applicationfound that the signal characteristic may be low, depending on the shapesof the pits provided on the super-resolution medium, even in a casewhere the amplitude of the RF signal becomes maximum. It is thereforenot assumed that while the super-resolution medium is reproduced by aconventional reproducing device by which a super-resolution medium is tobe reproduced, a spherical aberration is corrected by using, as a resultof evaluation of quality of a reproduction signal, an error rate ofaddress information detected by an address information error detectingsection. The inventors of the present application found that such amethod is used to correct the spherical aberration.

A reproducing device (300, 400) of a fourth aspect of the presentinvention is a reproducing device capable of reproducing content from anoptical information recording medium (optical disk 20) having (i) afirst region (data region 22) in which the content is recorded in a formof a first pit group including one or more pits shorter than an opticalsystem resolution limit of the reproducing device and (ii) a secondregion (medium information region 23) in which medium identificationinformation for distinguishing a type of the optical informationrecording medium is recorded in a form of a second pit group includingpits each having a length not less than the optical system resolutionlimit of the reproducing device, the reproducing device including: afirst spherical aberration correcting section (342) for, duringreproduction of the content recorded in the first region, carrying out aprocess of correcting, by using a result of evaluation of quality of areproduction signal indicative of the content, a spherical aberrationcaused by an irradiation section (optical pickup 6) for irradiating theoptical information recording medium with reproduction light; and asecond spherical aberration correcting section (343) for, duringreproduction of the medium identification information recorded in thesecond region, correcting, by carrying out a process different from theprocess to be carried out by the first spherical aberration correctingsection, the spherical aberration caused by the irradiation section.

As described above, according to the non-super-resolution medium, bycorrecting the spherical aberration based on the amplitude of the RFsignal, it is possible to reproduce the information while the signalcharacteristic is high. Meanwhile, however, according to thesuper-resolution medium, it may not be possible to reproduce theinformation while the signal characteristic is high. That is, asdescribed above, during reproduction of the super-resolution medium, thespherical aberration is corrected based on the result of the evaluationof the quality of the reproduction signal.

The optical information recording medium which is to be reproduced bythe reproducing device of the aspect of the present invention has thefirst region and the second region. The first region is a region inwhich the content is recorded in a form of first pit group including oneor more pits shorter than the optical system resolution limit of thereproducing device. That is, the first region is a super-resolutionregion in which information is reproducible by the super-resolutiontechnique. Meanwhile, the second region is a region in which the mediumidentification information for distinguishing a type of the opticalinformation recording medium is recorded in a form of second pit groupincluding pits each having a length not less than the optical systemresolution limit of the reproducing device. That is, the second regionis a non-super-resolution region in which information is unreproducibleby the super-resolution technique.

According to the reproducing device of the aspect of the presentinvention, during reproduction of the content recorded in the firstregion, which is the super-resolution region, the first sphericalaberration correcting section carries out the process of correcting thespherical aberration by using the result of the evaluation of thequality of the reproduction signal. Meanwhile, during reproduction ofthe medium identification information recorded in the second region,which is the non-super-resolution region, the second sphericalaberration correcting section corrects the spherical aberration bycarrying out the process different from the process to be carried out bythe first spherical aberration correcting section. Examples of theprocess different from the process to be carried out by the firstspherical aberration correcting section encompass correction of thespherical aberration by using the amplitude of the RF signal.

This makes it possible to reproduce, while a signal characteristic ishigh, each of (i) the content recorded in the first region(super-resolution region) and (ii) the medium identification informationrecorded in the second region (non-super-resolution region). Accordingto the aspect of the present invention, it is therefore possible toaccurately reproduce information, such as content, recorded inunspecified number of super-resolution regions of a super-resolutionmedium having both of a super-resolution region and anon-super-resolution region.

In a fifth aspect of the present invention, a reproducing device (300)is preferably arranged such that, in the fourth aspect of the presentinvention, The reproducing device as set forth in claim 4, furtherincluding a signal quality evaluating section (i-MLSE detecting section141, error rate detecting section 142) for evaluating quality of areproduction signal indicative of the content recorded in the firstregion, the first spherical aberration correcting section correcting, byusing a result of evaluation of the quality of the reproduction signalwhich quality has been evaluated by the signal quality evaluatingsection, the spherical aberration caused by the irradiation section, thesignal quality evaluating section being (i) an i-MLSE(Integrated-Maximum Likelihood Sequence Estimation) detecting section(141) for (a) detecting an i-MLSE which is an evaluation index forevaluating a signal characteristic of the reproduction signal and (b)evaluating the quality of the reproduction signal or (ii) an addressinformation error detecting section (error rate detecting section 142)for (a) detecting an error rate of address information contained in thereproduction signal and (b) evaluating the quality of the reproductionsignal.

With the arrangement, the signal quality evaluating section is thei-MLSE detecting section or the address information error detectingsection.

In a case where the signal quality evaluating section is the i-MLSEdetecting section, the i-MLSE can be used as the result of theevaluation of the quality of the reproduction signal. Accordingly,during reproduction of the first region (super-resolution region), it ispossible to correct a spherical aberration while a signal characteristicis sufficiently high.

Meanwhile, in a case where the signal quality evaluating section is theaddress information error detecting section, the error rate of addressinformation can be used as the result of the evaluation of the qualityof the reproduction signal.

As described in the third aspect, without providing, in the reproducingdevice, a new function (member, section) for evaluating quality of areproduction signal, it is possible to correct the spherical aberrationduring reproduction of the super-resolution region, by using the errorrate of the address information which error rate has been detected bythe address information error detecting section, while a signalcharacteristic is sufficiently high.

A reproducing device (400) of a sixth aspect of the present invention isa reproducing device capable of reproducing content from an opticalinformation recording medium (optical disk 20) having (i) a first region(data region 22) in which the content is recorded in a form of a firstpit group including one or more pits shorter than an optical systemresolution limit of the reproducing device and (ii) a second region(medium information region 23) in which manufacturer information forspecifying a manufacturer of the optical information recording medium isrecorded in a form of a second pit group including pits each having alength not less than the optical system resolution limit of thereproducing device, a plurality of manufacturers by each of which theoptical information recording medium is manufactured storing in advance,in the reproducing device, a first spherical aberration correcting value(spherical aberration correcting value R1) and a second sphericalaberration correcting value (spherical aberration correcting value R2)so that the first spherical aberration correcting value and the secondspherical aberration correcting value are associated with each of theplurality of manufacturers, the first spherical aberration correctingvalue being specified by using a result of evaluation of quality of areproduction signal indicative of the content recorded in the firstregion, the second spherical aberration correcting value (sphericalaberration correcting value R2) being specified by using an amplitude ofa reproduction signal indicative of the manufacturer informationrecorded in the second region, the reproducing device including: (i) adifference adjusting section (441) calculating a spherical aberrationcorrecting value (R) to be used during reproduction of the content, thespherical aberration correcting value (R) being calculated by adding, toa spherical aberration correcting value (RP) obtained when themanufacturer information has been read out from the second region, adifference (ΔR) between the first spherical aberration correcting valueand the second spherical aberration correcting value which areassociated with a manufacturer indicated by the manufacturer informationwhich has been read out from the second region; and (ii) a firstspherical aberration correcting section (342) for, during reproductionof the content recorded in the first region, correcting, by using aspherical aberration correcting value to be used during reproduction ofthe content, a spherical aberration caused by an irradiation section(optical pickup 6) for irradiating the optical information recordingmedium with reproduction light.

Accordingly, a difference between (i) a spherical aberration correctingvalue obtained when signal quality of a reproduction signal becomes bestduring reproduction of the first region and (ii) a spherical aberrationcorrecting value obtained when an amplitude of an RF signal becomesmaximum during reproduction of the second region depends on amanufacturer that manufactures the optical information recording medium.

With the arrangement, the reproducing device stores therein in advancethe first spherical aberration correcting value and the second sphericalaberration correcting value which are associated with each of theplurality of manufacturers. The difference adjusting section calculates,in the following manner, the spherical aberration correcting value to beused during reproduction of the content. That is, the differenceadjusting section calculates the spherical aberration correcting valueby adding, to the spherical aberration correcting value obtained whenthe manufacturer information has been read out from the second region,the difference between the first spherical aberration correcting valueand the second spherical aberration correcting value which have beenassociated with a manufacturer indicated by the manufacturer informationwhich has been read out from the optical information recording medium.During reproduction of the content, the first spherical aberrationcorrecting section corrects the spherical aberration by using thespherical aberration correcting value to be used during reproduction ofthe content which spherical aberration correcting value has beencalculated by the difference adjusting section.

Accordingly, during reproduction of the content, it is possible tocorrect the spherical aberration by merely providing the reproductiondevice with a difference adjusting section having a simpler function,without providing the reproduction device with a signal qualityevaluating section (i-MLSE detecting section, error rate detectingsection, etc.) for evaluating quality of a reproduction signalindicative of the content. According to the aspect of the presentinvention, it is therefore possible to accurately reproduce information,such as content, recorded in unspecified number of super-resolutionregions of a super-resolution medium having both of a super-resolutionregion and a non-super-resolution region.

A reproducing device (400) of a seventh aspect of the present inventionis a reproducing device capable of reproducing content from an opticalinformation recording medium (optical disk 20) having (i) a first region(data region 22) in which the content is recorded in a form of a firstpit group including one or more pits shorter than an optical systemresolution limit of the reproducing device and (ii) a second region(medium information region 23) in which manufacturer information forspecifying a manufacturer of the optical information recording medium isrecorded in a form of second pit group including pits each having alength not less than the optical system resolution limit of thereproducing device, a plurality of manufacturers by each of which theoptical information recording medium is manufactured storing in advance,in the reproducing device, difference information indicative of adifference (ΔR) between a first spherical aberration correcting value(spherical aberration correcting value R1) and a second sphericalaberration correcting value (spherical aberration correcting value R2)so that the first spherical aberration correcting value and the secondspherical aberration correcting value are associated with each of theplurality of manufacturers, the first spherical aberration correctingvalue being specified by using a result of evaluation of quality of areproduction signal indicative of the content recorded in the firstregion, the second spherical aberration correcting value (sphericalaberration correcting value R2) being specified by using an amplitude ofa reproduction signal indicative of the manufacturer informationrecorded in the second region, the reproducing device including: (i) adifference adjusting section calculating a spherical aberrationcorrecting value (R) to be used during reproduction of the content, thespherical aberration correcting value (R) being calculated by adding, toa spherical aberration correcting value (RP) obtained when themanufacturer information has been read out from the second region, thedifference indicated by the difference information which is associatedwith a manufacturer indicated by the manufacturer information which hasbeen read out from the second region; and (ii) a first sphericalaberration correcting section (342) for, during reproduction of thecontent recorded in the first region, correcting, by using a sphericalaberration correcting value to be used during reproduction of thecontent, a spherical aberration caused by an irradiation section(optical pickup 6) for irradiating the optical information recordingmedium with reproduction light.

With the arrangement, the reproducing device stores therein in advancethe difference information indicative of the difference between thefirst spherical aberration correcting value and the second sphericalaberration correcting value which are associated with each of theplurality of manufacturers. The difference adjusting section calculates,in the following manner, the spherical aberration correcting value to beused during reproduction of the content. That is, the differenceadjusting section calculates the spherical aberration correcting valueby adding, to the spherical aberration correcting value obtained whenthe manufacturer information has been read out from the second region,the difference indicated by the difference information which has beenassociated with a manufacturer indicated by the manufacturer informationwhich has been read out from the optical information recording medium.During reproduction of the content, the first spherical aberrationcorrecting section corrects the spherical aberration by using thespherical aberration correcting value to be used during reproduction ofthe content which spherical aberration correcting value has beencalculated by the difference adjusting section.

Accordingly, during reproduction of the content, it is possible tocorrect the spherical aberration by merely providing the reproductiondevice with a difference adjusting section having a simpler function,without providing the reproduction device with a signal qualityevaluating section (i-MLSE detecting section, error rate detectingsection, etc.) for evaluating quality of a reproduction signalindicative of the content. According to the aspect of the presentinvention, it is therefore possible to accurately reproduce information,such as content, recorded in unspecified number of super-resolutionregions of a super-resolution medium having both of a super-resolutionregion and a non-super-resolution region.

A reproducing device (500) of an eighth aspect of the present inventionis a reproducing device capable of reproducing content from an opticalinformation recording medium (optical disk 30) having (i) a first region(data region 22) in which the content is recorded in a form of a firstpit group including one or more pits shorter than an optical systemresolution limit of the reproducing device and (ii) a BCA (Burst CuttingArea) recording region (39) in which medium identification informationfor distinguishing a type of the optical information recording medium isrecorded in a stripe shape, the reproducing device including: a BCAreproduction control section (543) for reproducing the mediumidentification information recorded in the BCA recording region; and aspherical aberration correcting section (spherical aberration correctingsection 142, first spherical aberration correcting section 342) for,during reproduction of the content recorded in the first region,correcting, by using a result of evaluation of quality of a reproductionsignal indicative of the content, a spherical aberration caused by anirradiation section (optical pickup 6) for irradiating the opticalinformation recording medium with reproduction light.

With the arrangement, the optical information recording medium has theBCA recording region in which the medium identification information isrecorded in the stripe shape. The BCA reproduction control sectionreproduces the medium identification information from the BCA recordingregion.

The medium identification information recorded in the BCA recordingregion is formed, for example, in the stripe shape which is larger thana pit having a length not less than the optical system resolution limitof the reproducing device. This allows the BCA reproduction controlsection to read out the medium identification information withoutcarrying out processes such as (i) a process of correcting a sphericalaberration and (ii) a tracking process, unlike a case where the mediumidentification information is formed by pits.

According to the aspect of the present invention, it is thereforeunnecessary to carry out the processes in a case where the BCAreproduction control section reproduces the medium identificationinformation, and it is only necessary for the spherical aberrationcorrecting section to correct the spherical aberration duringreproduction of the content recorded in the first region. This makes itpossible to reduce a time period which is necessary to startreproduction of the information.

A reproducing method in accordance with a ninth aspect of the presentinvention is a method of controlling the reproducing device of the firstor second aspect of the present invention, the reproducing methodincluding the steps of: (a) irradiating the optical informationrecording medium with reproduction light; (b) converting, intoreproduction signal indicative of the content, light which reflected offthe optical information recording medium; (c) evaluating quality of thereproduction signal converted in the step (b); and (d) correcting aspherical aberration caused by the irradiation section, by using aresult of evaluation of the quality of the reproduction signal whichquality has been evaluated in the step (c).

With the arrangement, as with the first and second aspects, it ispossible to accurately reproduce information, such as content, recordedon unspecified number of super-resolution media.

A reproducing method in accordance with a tenth aspect of the presentinvention is a method of controlling (a method of reproducing) thereproducing device of the fourth aspect of the present invention, thereproducing method including the steps of: (a) during reproduction ofthe content recorded in the first region, carrying out a process ofcorrecting, by using a result of evaluation of quality of a reproductionsignal indicative of the content, a spherical aberration caused by anirradiation section for irradiating the optical information recordingmedium with reproduction light; and (b) during reproduction of themedium identification information recorded in the second region,correcting, by carrying out a process different from the process to becarried out in the step (a), the spherical aberration caused by theirradiation section.

With the arrangement, it is possible to accurately reproduceinformation, such as content, recorded in unspecified number ofsuper-resolution regions of a super-resolution medium having both of afirst region (super-resolution region) and a second region(non-super-resolution region).

A reproducing device in accordance with an eleventh aspect of thepresent invention is a reproducing device capable of reproducing contentfrom an optical information recording medium in which the content isrecorded in a form of a pit group including one or more pits shorterthan an optical system resolution limit of the reproducing device, thereproducing device including: a signal quality evaluating section forevaluating quality of a reproduction signal which (i) has been generatedbased on reproduction light with which the optical information recordingmedium has been irradiated and (ii) is indicative of the content; and aspherical aberration correcting section for correcting, by using aresult of evaluation of the quality of the reproduction signal whichquality has been evaluated by the signal quality evaluating section, aspherical aberration caused by an irradiation section for irradiatingthe optical information recording medium with reproduction light.

With the arrangement, as with the first aspect, it is possible toaccurately reproduce information, such as content, recorded onunspecified number of super-resolution media.

The reproducing device in accordance with the foregoing aspects of thepresent invention may be realized by a computer. In this case, thepresent invention encompasses: a control program for the reproducingdevice which program causes a computer to operate as each section of thereproducing device so that the reproducing device can be realized by thecomputer; and a computer-readable storage medium storing therein thecontrol program.

[Miscellaneous Descriptions]

Note that an aspect of the present invention can be described as below.

(1) An optical information recording medium reproducing device inaccordance with an aspect of the present invention is a reproducingdevice for reproducing content to be used by a user, from a read-onlyoptical information recording medium in which the content to be used bythe user is recorded in a form of pit group including one or more pitsshorter than an optical system resolution limit of a reproducing opticalsystem of the corresponding reproducing device, the reproducing deviceincluding: an irradiation section for irradiating the read-only opticalinformation recording medium with reproduction light; a conversionsection for converting, into a signal, light which reflected off theread-only optical information recording medium and is obtained by theirradiation section; a signal quality evaluating section for evaluatingquality of the signal obtained by the conversion section; and a signalquality-based spherical aberration correcting section for correcting aspherical aberration caused by the irradiation section, by use of thesignal quality evaluating section.

(2) An optical information recording medium reproducing device inaccordance with an aspect of the present invention is a reproducingdevice for reproducing content to be used by a user, by irradiating, viaan objective lens having a numerical aperture of 0.85, an opticalinformation recording medium with reproduction light having a wavelengthof 405 nm, the optical information recording medium including (a) alight transmitting layer having a surface which the reproduction lightenters, (b) an information recording layer, and (c) a substrate, thelight transmitting layer, the information recording layer, and thesubstrate being provided in this order from a side from which thereproduction light enters, the content to be used by the user, beingrecorded in the information recording layer by use of a pre-pit group(i) which is provided on the substrate in a scanning direction of thereproducing device, the pre-pit group including one or more pre-pitsshorter than 119 nm which is an optical system resolution limit of thereproducing device, the reproducing device including: an irradiationsection for irradiating the read-only optical information recordingmedium with reproduction light; a conversion section for converting,into a signal, light which reflected with the optical informationrecording medium and is obtained by the irradiation section; a signalquality evaluating section for evaluating quality of the signal obtainedby the conversion section; and a signal quality-based sphericalaberration correcting section for correcting a spherical aberrationcaused by the irradiation section, by use of the signal qualityevaluating section.

(3) In an aspect of the present invention, an optical informationrecording medium reproducing device can be arranged such that, in (1) or(2), the signal quality evaluating section is (i) an i-MLSE detectingsection for detecting an i-MLSE from a reproduction signal or (ii) anaddress information error detecting section for (a) extracting onlyaddress information from a reproduction signal and (b) detecting anerror rate of only the address information.

(4) An optical information recording medium reproducing device inaccordance with an aspect of the present invention is a reproducingdevice for reproducing content to be used by a user, from an opticalinformation recording medium having (i) a first region in which thecontent to be used by the user is recorded in a form of pit groupincluding one or more pits shorter than an optical system resolutionlimit of a reproducing optical system of the corresponding reproducingdevice and (ii) a second region in which medium identificationinformation for distinguishing a type of the optical informationrecording medium is recorded in a form of pit group including only pitslonger than the optical system resolution limit of the reproducingoptical system of the corresponding reproducing device, a firstspherical aberration correcting section to be used during reproductionof the first region differing from a second spherical aberrationcorrecting section to be used during reproduction of the second region.

(5) In an aspect of the present invention, an optical informationrecording medium reproducing device can be arranged such that, in (4),the first spherical aberration correcting section is (i) an i-MLSEdetecting section for detecting an i-MLSE from a reproduction signal or(ii) an address information error detecting section for (a) extractingonly address information from a reproduction signal and (b) detecting anerror rate of only the address information.

The present invention is not limited to the embodiments, but can bealtered by a skilled person in the art within the scope of the claims.An embodiment derived from a proper combination of technical means eachdisclosed in a different embodiment is also encompassed in the technicalscope of the present invention. Further, it is possible to form a newtechnical feature by combining the technical means disclosed in therespective embodiments.

INDUSTRIAL APPLICABILITY

The present invention is applicable to a super-resolution medium.

REFERENCE SIGNS LIST

1: Optical disk (optical information recording medium)

A: Optical disk (optical information recording medium)

B: Optical disk (optical information recording medium)

2: Substrate

3: Information recording layer

4: Light transmitting layer

6: Optical pickup (irradiation section)

9: RF signal processing circuit (conversion section)

20: Optical disk (optical information recording medium)

22: Data region (first region)

23: Medium information region (second region)

30: Optical disk (optical information recording medium)

100: Reproducing device

141: i-MLSE detecting section (signal quality evaluating section)

142: Spherical aberration correcting section

200: Reproducing device

241: Error rate detecting section (signal quality evaluating section,address information error detecting section)

300: Reproducing device

342: First spherical aberration correcting section

343: Second spherical aberration correcting section

660: Objective lens

1. A reproducing device capable of reproducing content from an opticalinformation recording medium in which the content is recorded in a formof a pit group including one or more pits shorter than an optical systemresolution limit of the reproducing device, comprising: an irradiationsection for irradiating the optical information recording medium withreproduction light; a conversion section for converting, intoreproduction signal indicative of the content, light which reflected offthe optical information recording medium; a signal quality evaluatingsection for evaluating quality of the reproduction signal converted bythe conversion section; and a spherical aberration correcting sectionfor correcting a spherical aberration caused by the irradiation section,by using a result of evaluation of the quality of the reproductionsignal which quality has been evaluated by the signal quality evaluatingsection; wherein the signal quality evaluating section is an i-MLSE(Integrated-Maximum Likelihood Sequence Estimation) detecting sectionfor (a) detecting an i-MLSE which is an evaluation index for evaluatinga signal characteristic of the reproduction signal and (b) evaluatingquality of the reproduction signal, it is determined whether the opticalinformation recording medium is a super-resolution medium or aconventional medium, and in a case where the optical informationrecording medium is determined to be the super-resolution medium, theoptical information recording medium is irradiated with the reproductionlight having reproduction power for super-resolution reproduction.
 2. Areproducing device capable of reproducing content by irradiating, via anobjective lens having a numerical aperture of 0.85, an opticalinformation recording medium with reproduction light having a wavelengthof 405 nm, the optical information recording medium including (a) alight transmitting layer having a surface which the reproduction lightenters, (b) an information recording layer which the reproduction lightreflects off so that information is reproduced, and (c) a substrate onwhich a pit group is provided in a scanning direction, the pit groupincluding one or more pits shorter than 119 nm which is an opticalsystem resolution limit of the reproducing device, the lighttransmitting layer, the information recording layer, and the substratebeing provided in this order from a side from which the reproductionlight enters, the content being recorded in the information recordinglayer by use of the pit group, comprising: an irradiation section forirradiating the optical information recording medium with reproductionlight; a conversion section for converting, into reproduction signalindicative of the content, light which reflected off the opticalinformation recording medium; a signal quality evaluating section forevaluating quality of the reproduction signal converted by theconversion section; and a spherical aberration correcting section forcorrecting a spherical aberration caused by the irradiation section, byusing a result of evaluation of the quality of the reproduction signalwhich quality has been evaluated by the signal quality evaluatingsection; wherein the signal quality evaluating section is an i-MLSE(Integrated-Maximum Likelihood Sequence Estimation) detecting sectionfor (a) detecting an i-MLSE which is an evaluation index for evaluatinga signal characteristic of the reproduction signal and (b) evaluatingquality of the reproduction signal, it is determined whether the opticalinformation recording medium is a super-resolution medium or aconventional medium, and in a case where the optical informationrecording medium is determined to be the super-resolution medium, theoptical information recording medium is irradiated with the reproductionlight having reproduction power for super-resolution reproduction.